Astronomy & Astrophysics manuscript no. aanda c ESO 2019 July 17, 2019

The HST Key Project galaxies NGC 1326A, NGC 1425 and NGC 4548: New variable stars and massive star population Z.T. Spetsieri1, 2, A.Z. Bonanos1, M. Yang1, M. Kourniotis3, D. Hatzidimitriou2, 1

1 IAASARS, National Observatory of Athens, 15236 Penteli, Greece e-mail: [email protected] 2 Department of Astrophysics, Astronomy & Mechanics, Faculty of Physics, University of Athens, 15783 Athens, Greece 3 Astronomický ústav, Akademie vedˇ Ceskéˇ republiky, Fricovaˇ 298, 251 65 Ondrejov,ˇ Czech Republic

July 17, 2019

ABSTRACT

Studies on the massive star population in galaxies beyond the Local Group are the key to understand the link between their numbers and modes of star formation in different environments. We present the analysis of the massive star population of the galaxies NGC 1326A, NGC 1425 and NGC 4548 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in the F555W and F814W filters. Through high precision point spread function fitting photometry for all sources in the three fields we identified 7640 candidate blue supergiants, 2314 candidate yellow supergiants, and 4270 candidate red supergiants. We provide an estimation the ratio of blue to red supergiants for each field as a function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics (MESA) at solar metallicity, we defined the luminosity function and estimated the star formation history of each galaxy. We carried out a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range, and the inverse von-Neumann ratio. This analysis yielded 243 new variable candidates with absolute magnitudes ranging from MV = −4 to −10 mag. We classified the variable stars based on their absolute magnitude and their position on the color-magnitude diagram using the MESA evolutionary tracks at solar metallicity. Our analysis yielded 8 candidate variable blue supergiants, 12 candidate variable yellow supergiants, 21 candidate variable red supergiants, and 4 candidate periodic variables. Key words. galaxies: individual: NGC 1326A–galaxies: individual: NGC 1425–galaxies: individual: NGC 4548 – stars: massive- stars –stars: evolution – stars: supergiants –stars: variables

1. Introduction gives us the opportunity to study in detail the stellar population of blue supergiants (BSGs), yellow supergiants (YSGs) and red Variability studies at large distances can be used as a powerful supergiants (RSGs) in galaxies beyond 10 Mpc. Studying mas- tool to study the pre-supernova state and evolved states of mas- sive stars at larger distances is the key to understand whether sive stars (Kochanek et al. 2017). The open questions of stellar the evolution of massive stars is different in different environ- evolution regarding mass loss, internal mixing and stellar winds ments. For example, the ratio of the BSGs to RSGs (B/R ratio) (Langer 2012; Massey 2003) have been frequently investigated as a function of metallicity and galactocentric radius, is among in conjunction with photometric variability studies (Bonanos the diagnostic tools applied to study metallicity, star formation, 2007; Yang & Jiang 2012; Kourniotis et al. 2017; Soraisam et al. mass loss and convection processes (Brunish et al. 1986; Langer 2018). The evolution of very massive stars is quite uncertain & Maeder 1995). Our previous study on the massive star pop- both due to the limited observational samples and physical pro- ulation of the Virgo cluster galaxy NGC 4535 (Spetsieri et al. cesses that trigger variability. For example, the origin of variabil- 2018, Paper I) demonstrates the importance of archival HST data ity in the light curves of luminous blue variables (LBVs) in metal for extra-galactic studies on massive stars. NGC 4535 was stud- poor environments (Kalari et al. 2018), the physical mechanisms ied by Macri et al. (1999) for Cepheid variables as part of the causing shear-induced instabilities in massive stars (Maeder & HST Key project and 50 Cepheid variables were detected. Us- Meynet 2000; Heger & Langer 2000) or evolutionary paths lead- ing data from the HST we conducted our own photometry for ing to binarity in yellow and red supergiants (Prieto et al. 2008; NGC 4535 aiming to the identification of more massive variable arXiv:1907.07140v1 [astro-ph.SR] 15 Jul 2019 Moriya 2018) are some of the open questions that are yet to be stars. Our study unveiled 120 new variable massive stars among investigated. The short evolution timescale, combined with the which eight luminous candidate RSGs, four candidate YSGs and rarity of massive stars are the biggest challenges in testing stel- one candidate LBV. lar evolutionary models against observations. A solution to over- In this study we aim to expand our search for massive stars, come the problem of the limited observational sample of massive using the same method adopted in Paper I to three other galax- stars is to take advantage of the large amount of existing archival ies studied in the HST Key project: NGC 1326A (Prosser et al. data. 1999), NGC 1425 (Mould et al. 2000) and the Virgo Cluster Archival data from the HST allow us to extend the studies of galaxy NGC 4548 (Graham et al. 1999). All three fields were massive stars and trace star formation beyond the Local Group. previously studied for Cepheid variables with 15 Cepheids re- Archives are widely recognized as a valuable resource for astron- ported in NGC 1326A, 20 in NGC 1425, and 24 in NGC 4548. omy. The large sample of deep extragalactic HST observations, However, the existence of other objects that were not classified

Article number, page 1 of 28 A&A proofs: manuscript no. aanda as Cepheids but showed variability in their light curve (Graham error was estimated using bins of 0.15 mag, within 0.05 to 0.06 et al. 1999) is yet to be investigated. These three galaxies were mag in V and 0.04 to 0.05 mag in I. The number of stars used for selected as metal rich galaxies with high star formation rates that the artificial star tests did not cause overcrowding as the program can help in providing a better view of the variability displayed in measured one star at the time. Fig. 1 shows a histogram with the the massive star population as massive stars serve as the primary magnitudes of the sources of each galaxy after the photometric source of carbon, nitrogen, and oxygen (CNO) enrichment of quality cuts. Fig. 2 shows an example of the mean magnitude the interstellar medium (ISM) and are progenitors of supernovae in the V filter as a function of the difference in magnitude be- (Conroy et al. 2018; Maeder et al. 1980). tween the artificial stars inserted and the ones recovered for each The paper is structured as follows, the observations and data galaxy. The 50% completeness factor in V and I bands, measured reduction are presented in Section 2, the massive star popula- from the artificial star tests occurs at ∼ 26.8 mag and 26.0 mag tion of NGC 1326A, NGC 1425, NGC 4548 and the blue to red in NGC 1326A, ∼ 26.9 mag and ∼ 26.2 mag in NGC 1425, and supergiant ratio are described in Section 3. The selection of vari- ∼ 26.5 mag and ∼ 25.8 mag in NGC 4548 respectively. Astrom- able candidates and the classification of the new massive vari- etry was performed by using the Hubble Source Catalog (HSC) able candidates are given in Section 4. The summary is given in version 3 (Whitmore et al. 2016) 2 and applying the astrometric Section 5. correction suggested by Anderson & King (2000) and described in detail in Paper I. We used stars from the HSC at various posi- tions across each chip to calculate the transformations from the 2. Observations and reduction X, Y positions to the RA, Dec. Relative positions are good to ∼ 0.05 arcsec, while the accuracy of the absolute positions is 2.1. Observations limited by the HST coordinates, which are constrained by the We used archival observations of NGC 1326A, NGC 1425, and accuracy of the HST guide star catalog to ∼ 0.100. NGC 4548 taken with the HST WFPC2 as described in Freed- man et al. (2001) as part of the HST Key Project. For the three galaxies, we used the observations available in the filters F555W (equivalent to Johnson V filter) and the F814W (equivalent to 3. Massive star population Kron-Cousins I). In particular, we used 13 epochs of observa- 3.1. Identification of the massive star candidates tions in F555W and 8 epochs in F814W that are available for the galaxies NGC 1326A and NGC 4548, while for NGC 1425, We examined the massive star population in each field using we used the 14 available epochs in F555W and 8 in F814W . color and magnitude criteria to determine the blue, yellow, and The F555W data consisted of 3x1200 sec exposures and 4x1300 red supergiant regions. sec exposures, while the F814W data consisted of 3x1300 sec Figures 3 to 5 show the V−I versus MV CMD, for the stars exposures. Data were collected at four dithering positions, with that passed the quality tests mentioned in Sect. 2, based on the one quarter of the observations (four pairs of F814W images and distance modulus of each field (see Table 5). The error-bars two pairs of F555W images) taken at each position. We retrieved shown were derived from the artificial star tests. The total fore- the pre-reduced images through the Mikulsky Archive for Space ground interstellar reddening is E(V−I)= 0.15 ± 0.04 mag in Telescopes1 and performed point spread function (PSF) photom- NGC 1326A, E(V−I)= 0.16 ± 0.03 mag in NGC 1425, and etry using the latest WFPC2 module of DOLPHOT (updated in E(V−I)= 0.18 ± 0.04 mag in NGC 4548 (Freedman et al. 2001). 2016), which is a modified version of HSTphot (Dolphin 2000). The faint limit in each field corresponds to the V magnitude up to which our sample reaches 50% completeness, as at this magni- tude the photometric errors do not exceed 0.1 mag. We adopted 2.2. Reduction the color and magnitude criteria by Grammer & Humphreys We proceeded with the photometric reduction as described in the (2013) to separate the regions of BSG, YSGs, and RSGs. The manual of the WFPC2 module of DOLPHOT and in Paper I. We three populations for each field range from: applied the photometric quality criteria listed in the DOLPHOT manual to distinguish the isolated, point-like sources from the DOLPHOT ≥ extended sources detected by . The criteria are: S/N NGC 1326A 10, −0.3≤ sharpness ≤0.3, χ2 ≤ 2.5 and Object type=1. The re- sulting catalog for each field includes the coordinates of each BSGs: (V−I) ≤ 0.25 mag 21.5 ≤ V ≤ 25.5 mag source in RA, Dec (J2000), X, Y, and mean magnitude in V and (V−I) ≤ 0.60 mag 25.5 < V ≤ 26.8 mag I filters. The total number of stars after the quality cuts are: 5897 YSGs: 0.25 < (V−I) ≤ 0.6 mag 21.5 ≤ V ≤ 25.5 mag stars in NGC 1326A, 5232 stars in NGC 1425, and 5790 stars in 0.6 < (V−I) ≤ 1.3 mag 21.5 < V ≤ 26.8 mag − NGC 4548. Tables 1 3 present the first 10 entries of each cata- RSGs: (V−I) > 1.3 mag 21.5 ≤ V ≤ 26.8 mag log listing the ID, RA (J2000), Dec (J2000), X, Y mean magni- tudes and magnitude errors in V and I. The catalogs for the three galaxies are available in a machine-readable form at the Centre NGC 1425 de Données Astronomiques de Strasbourg (CDS). We estimated the photometric errors and completeness by BSGs: (V−I) ≤ 0.25 mag 21.5 ≤ V ≤ 25.3 mag conducting artificial star tests as described in Lianou & Cole (V−I) ≤ 0.60 mag 25.3 < V ≤ 26.9 mag (2013). The magnitude and errors of the artificial stars inserted in YSGs: 0.25 < (V−I) ≤ 0.6 mag 21.5 ≤ V ≤ 25.3 mag each field were measured at the same time as the field stars. We 0.6 < (V−I) ≤ 1.3 mag 21.5 < V ≤ 26.9 mag ran the tests injecting 5000 stars per chip ranging in magnitude RSGs: (V−I) > 1.3 mag 21.5 ≤ V ≤ 26.9 mag from 19 to 27 mag in both filters for all three fields. The mean

1 http://archive.stsci.edu/hst/search.php 2 http://archive.stsci.edu/hst/hsc/

Article number, page 2 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

and NGC 4548, and assumed that the center of the galaxy is the NGC 4548 region with the highest metallicity. The variation of the number of blue to red supergiants with metallicity is a test for stellar evo- BSGs: (V−I) ≤ 0.25 mag 20.5 ≤ V ≤ 24.5 mag lutionary models as it is highly linked with star formation events (V−I) ≤ 0.60 mag 24.5 < V ≤ 26.5 mag and star formation history (Langer 2012). In areas with small YSGs: 0.25 < (V−I) ≤ 0.6 mag 20.5 ≤ V ≤ 24.5 mag coverage, variations in the B/R ratio can occur due to photomet- 0.6 < (V−I) ≤ 1.3 mag 20.5 < V ≤ 26.5 mag ric errors and reddening in the outer regions of the field, how- RSGs: (V−I) > 1.3 mag 20.5 ≤ V ≤ 26.5mag ever, we have eliminated this possibility, as we normalized our distances to the center of each field using galactic coordinates. In total we identified 7640 candidate BSGs (2652 in NGC Hence, the increase of metallicity with galactocentric radius is 1326A, 2833 NGC 1425, and 2155 in NGC 4548), 2314 candi- less likely to be due to systematic errors coming from reddening date YSGs (868 in NGC 1326A, 939 in NGC 1425, and 507 in and photometry. NGC 4548), and 4270 candidate RSGs (1868 in NGC 1326A, Our results are in agreement with our previous work on the 1281 in NGC 1425, and 1121 in NGC 4548). massive star population in the Virgo Cluster Galaxy NGC 4535 We estimated the foreground contamination in the direction in Paper I and in M101 (Grammer & Humphreys 2013). The of the three fields through the Besançon Galactic population syn- observations of M101 (Grammer & Humphreys 2013) covered thesis model (Robin et al. 2003) and found that the majority the whole galaxy, while in this study the WFPC2 field of view of the foreground stars lie in the YSG and RSG regions. Fore- only covered about a quarter of the galaxy. However, the radial ground contamination has always been among the challenges decline of the B/R ratio with decreasing metallicity is common in the identification of luminous massive stars such as YSGs in all fields, confirming the trend already presented by previous and RSGs as these types of stars have similar magnitudes as studies (Eggenberger et al. 2002; Maeder et al. 1980). Milky Way stars. Photometric errors near the completeness lim- its could also cause contamination, e.g. by YSGs that are part of 3.3. Luminosity function and star formation rate the neighboring RSG population due to reddening, and extinc- tion. We used the Modules for Experiments in Stellar Astrophysics Table 4 lists the properties (inclination, distance, distance (MESA) Isochrones and Stellar Tracks (Choi et al. 2016, MIST;) modulus, metallicity, mophological type, redshift and absolute at the metallicity of each galaxy (see Table 5), to estimate the magnitude) of NGC 1326A, NGC 1425, and NGC 4548. Ta- evolutionary state of the massive stars. We used the method de- ble 5 includes: the galaxy name, the numbers of candidate BSGs, scribed in Dohm-Palmer et al. (1997) to derive the V luminosity YSGs, RSGs, along with those of their variable counterparts. As function for the blue helium-burning stars (blue HeB stars) in shown in Table 5 the galaxy with the highest foreground contam- NGC 1326A, NGC 1425 and NGC 4548. For each field we set ination is NGC 4548, followed by NGC 1425 and NGC 1326A. magnitude bins of equal magnitude (0.18 mag) from MV = −3.8 up to −9 mag for NGC 1326A, NGC 1425, and NGC 4548 (i.e. the magnitude where the sample reaches 50 % completeness). 3.2. Blue to red supergiant ratio The models indicate sources within the age of 5-100 Myrs. The We calculated the de-projected distances of the luminous stars luminosity function of the blue HeB stars in the V band in all with respect to the center of each field taking into account the three fields is plotted in Fig. 7 (right column). The errors were inclination angle of each galaxy (see Table 5). We split the mas- derived by the artificial star tests, while error propagation has sive stars in three groups: BSGs, YSGs, and RSGs, based on the been also used from one bin to another. The numbers plotted color and magnitude criteria described in Section 3.1. We set ten above the luminosity function are the ages of the isochrones in annuli of equal distance from the center of the galaxy, normal- Myrs based on the MESA models. In order to estimate the star ized the number of BSGs, YSGs, and RSGs to the same area formation rate based on the counts given from the luminosity taking into account the foreground contamination of each field, function, we made use of the equation given in Dohm-Palmer and propagated the related errors to calculate the B/R ratio. The et al. (1997). spatial distribution of the BSGs and RSGs within the annuli in each field is shown in the right column of Fig. 6. The left column Z logm2 Z t2(logm) of Fig.6 shows the trend of the B/R ratio versus galactocentric ra- C(MV , V − I) = φ(logm, t) × R(t)dtdlogm (1) dius in NGC 1326A, NGC 1425, and NGC 4548. The B/R ratio logm1 t1(logm) in all galaxies declines radially indicating an evident drop of the number of BSGs at the outer regions of the field. The exponential adjusted for the stars, where φ is the initial mass function (IMF) decline of the B/R ratio in the first panel of Fig 6 is misleading normalized to unity, m is mass, R is the star formation rate in −1 as it is basically caused by the first data point that corresponds units of M yr , and t is time. We used the Salpeter slope for to the center of NGC 1326A which is included in the image of the IMF and the normalized IMF is the galaxy. In NGC 4548 the B/R ratio shows a decreasing trend with a rise in the number of blue supergiants occurring at the m −1.35 sixth annulus (1.430). This rise may be explained by the coincid- φ(logm)dlogm = 0.394( ) dlogm (2) M ing of the annulus with the spiral arm of the field, where a larger number of BSGs are located due high gas and dust accumulation. For each galaxy we derived the area of the filed of view of our A declining B/R ratio with increasing radius has been reported observations to find the SFR/kpc2. The SFR/kpc2 is shown in by previous studies (Humphreys & Sandage 1980; Eggenberger Fig. 7. et al. 2002; Spetsieri et al. 2018) and has been linked with the The star formation history of NGC 1326A shows a gradual −2 radial changes of the metallicity of the field. We compared our increase in look-back time at M kpc indicating high star for- results on the B/R ratio with our previous study and the study mation rates over the past 70 Myrs. In NGC 1425 the star forma- of Grammer & Humphreys (2013) for NGC 1326A, NGC 1425 tion history reveals a recent peak ∼ 10 Myrs followed by a drop,

Article number, page 3 of 28 A&A proofs: manuscript no. aanda which could be a sign of a star formation event. The high number variable in either of the three variability indexes and digit 0 for of YSGs in NGC 1425 presented in Table 5 could explain a star the sources that were not selected as variables by an index. In the formation event over which massive stars formed and evolved si- case that a star is flagged as variable in only one index and filter, multaneously. The star formation rate appears constant between we assume that it could be due to the wavelength-dependence of 25-40 Myrs and increases between 40-70 Myrs. From 70-100 variability, or due to the sensitivity of the index to the type of the Myrs there is no significant variation in the star formation his- variability displayed. tory. The field with the highest star formation rate is the Virgo Among the variable sources primarily detected by the algo- Cluster Galaxy NGC 4548. The star formation rate in NGC 4548 rithm were the published Cepheids of the three fields. In particu- indicates a constant increase with small fluctuations between 5 lar, there were 15 reported Cepheids in NGC 1326A, 20 in NGC and 65 Myrs with the star formation rate reaching its peak at 1425 and 24 in NGC 4548. These sources, are not included in −2 9000 M kpc at 70 Myrs. Between 75 and 100 Myrs the star Tables 6 − 10 as they are known sources, however, we used the formation rate shows a slight decrease. NGC 4548 has the largest mean magnitudes by Prosser et al. (1999); Mould et al. (2000); estimated value of metallicity compared to the other two fields. Graham et al. (1999) to test the quality of our photometry. We This could be an indication of how star formation proceeds as a found a negligible discrepancy between the latter studies and our function of metallicity, since the role of massive stars regarding measurements. The differences in magnitude are namely 0.015 ± star formation remains unclear. The recent star formation history 0.004 mag for NGC 1326A, 0.033 ± 0.009 mag for NGC 1425, estimated for the three fields does not show signs of significant and 0.018 ± 0.006 mag for NGC 4548. star burst events that could result in the formation of 100 M All variables in all three fields were identified by MAD in at stars. As massive stars are characterized by their brief lifetimes least one filter, while 211 out of 243 variables were detected in we do not rule out the existence of stars more massive than 30 at least one filter in IQR. The inverse von-Neumann ratio index M , as they may have evolved and exploded by the time of the is mostly sensitive to correlation-based than scatter-based obser- observations. Additionally, very young massive stars are born in vations and 37% of the variable candidates were selected by this highly contaminated star forming regions. As a result, resolving index. such stars photometrically is challenging as they may appear as We used MESA evolutionary tracks to estimate the masses diffuse or blended sources. of the new variables in each field. The models were generated assuming rotation at 40% of the critical speed and values of metallicity for each field based on Freedman et al. (2001). We 4. Variability adopted solar metallicity for NGC 1326A and super-solar values After identifying the massive stars in the three fields our next for metallicity, for NGC 1425 and NGC 4548. Figs. 3, 4 and 5 step was to investigate whether those sources displayed any type show both the CMDs and finder charts of the new candidate vari- of variability. We adopted the methodology described in Paper I ables and evolutionary tracks over-plotted along with the spatial and considered only the stars with more than five measurements distribution of the candidate variable stars for each galaxy, re- in either the V or I filters. We used the three variability indexes spectively. The masses corresponding to the tracks span from described in Paper I: the median absolute deviation (MAD), the ∼ 8−20 M and the magnitude ranges from −3.8 mag −9 mag. interquartile range (IQR), and the inverse von Neumann ratio The error bars correspond to the uncertainty due to reddening (1/η) (Sokolovsky et al. 2017). E(V−I), photometric errors and the distance modulus. We took The variability indexes were measured in each one of the in to account the E(V−I) reddening in each field, derived the WFPC2 chips in all three fields. To derive the variability indexes reddening vector based on the E(V−I) values mentioned in Sec- we sorted the sources included in each WFPC2 chip by increas- tion 3.1, and adopted a ratio of total to selective absorption RV = ing magnitude and set bins with at least 5% of the total number AV /(AV − AI) =3.1 (Cardelli et al. 1989; Freedman et al. 2001). of sources per bin to maintain statistical significance. For each The evolutionary tracks shown in each plot correspond to 8, 10, bin, we calculated the median value of the index and the standard 15 and 20 M for the metallicities implied by Freedman et al. deviation (σ), we set a 4σ threshold and considered as variable (2001). The degeneracy of the evolutionary tracks of different candidates all sources above that threshold in either F555W or M does not allow us to make a solid estimation of the mass of F814W. Fig. 8 shows an example of the index versus magnitude the candidate massive stars. For example in Figure 5 the 8 M diagram for the MAD, in the WF3 chip of WFPC2 in the V filter track overlaps with the 10 M track, making it challenging to dis- for NGC 1326A, NGC 1425, and NGC 4548. Candidate variable tinguish stars within that mass range. However, the mass range sources are shown as red squares while the known Cepheids are proposed for the candidate massive stars seems fully compliant shown as blue triangles. All published Cepheid variables in all with the values of metallicity and extinction of each field. three fields were recovered by our algorithm. We created index Based on the colors (V−I) and mass range of the published vs. magnitude plots for all chips in all three galaxies and deter- variables shown in Fig. 3, 4 and 5 we proceed to classify the mined the final number of variables. newly discovered candidate massive variable stars. In the three The total number of new variable candidates is 243, which fields, the new candidate variables lie between ∼ 8−20 M , while are distributed as follows: 48 variable candidates in NGC 1326A, in NGC 1326A 17 out of the 48 newly identified candidate vari- 102 in NGC 1425 and 93 in NGC 4548. We present light curves ables display masses below 8 M . The majority of the variable for all the new variable candidates identified in Figs. 9−11. The stars in the fields show V−I colors between −0.5 to 2.5 mag. The figures show that the variable candidates vary with the same CMD in Fig. 3 displays fewer candidate massive variable stars, trend in both filters and display variations of similar ampli- compared to the CMDs in Figs. 4 and 5. This is explained by the tude. Tables 6 to 10 contain the full list with IDs, coordinates, different parts of each galaxy covered during the observations of mean magnitude, magnitude errors, variability indexes, HSC v3 the HST Key Project. In NGC 1425 and NGC 4548 the obser- MatchIDs and notes of the variables in all three fields. The ta- vations cover a larger part of the spiral arms compared to NGC bles also include the amplitude of variability and classification 1326A. based on their V−I color and mass as estimated by the models. In Tables 6 − 10 we use digit 1 to flag the sources that appeared

Article number, page 4 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

The subsections below provide information about the new M and Te f f ∼ 7000K. Based on its characteristics, this source variable candidate BSGs, YSGs and RSGs identified in the three is classified as a candidate variable YSG/YHG. Variability in galaxies. YSGs, has been previously reported in the studies of Humphreys & Davidson (1979); Percy & Kim (2014); Humphreys et al. (2016); Kourniotis et al. (2017); Spetsieri et al. (2018), in the 4.1. Candidate variable red supergiants region with M ≥ 20 M and log L/Lo > 5.4. and is typical of Our analysis yielded in total 21 candidate variable RSGs, three in amplitude 0.3-0.6 magnitudes similar to the amplitude of V1. As NGC 1326A, six in NGC 1425 and ten in NGC 4548. The mag- spectroscopic classification is essential for accurate discrimina- nitude range of the candidates is −7.0 ≤ MV ≤ −4.0 mag and the tion between YHGs and YSGs, we cannot further infer on the V−I index is within 1.6−2.1 mag. According to the MESA mod- state of our yellow stars. els, the masses and temperatures of the stars are between 8−16 M and 3000 < Te f f < 4000 K. However, stars between 7 M 4.3. Candidate variable blue supergiants and 8 M may also be super-AGB stars (Becker & Iben 1980; Groenewegen & Sloan 2018). Super-AGB stars are equally lu- Among the candidate variable massive stars identified in the minous to RSGs and with a similar color, making it difficult to three fields are 8 blue supergiants. We expect no foreground distinguish sources of those two types given the uncertainty in contamination in that region, according to the Besançon models. distance. The basic feature used to identify RSGs is their bolo- The mass range implied by the models for the candidate variable metric magnitude, (Mbol ≤ −7.1 mag) (Wood et al. 1983). How- BSGs is 15 to 20 M , the magnitudes range between −8 < MV ever, stars with MV < −7 mag displaying masses above 16 M < −4.9 mag, and the temperatures, based on the models, range are less likely to be super-AGB stars. from 5900< Te f f <17400 K. The field with the largest number Although most RSGs do not usually show variability or pe- of BSGs (64) is the Virgo Cluster galaxy NGC 4548. As shown riodic variability, the candidate RSGs in the three fields vary in section 3.3 this galaxy is considered to be star forming. The in both filters and in some cases display amplitudes between amplitude of variability of the BSGs reaches 1.2 mag for the 0.2-0.6 mag. The studies of Yang & Jiang (2012) and Yang low-mass candidate BSGs (e.g. V97 in NGC 1425) and 0.1 mag et al. (2018) have studied periodic variability of the RSGs in for brighter and more massive BSGs (e.g. V7 in NGC 1425). the LMC and SMC, howevwer, in our case it is difficult to de- The existence of a large number of BSGs in a galaxy is in- fine a period for the light curve of the candidate RSGs due to dicative of recent star formation as BSGs are young stellar ob- the small timescale and the low number of observations. Based jects that are found in the galactic spiral arms in regions rich in on the studies of Levesque et al. (2006), Szczygieł et al. (2010), gas and dust. Based on stellar evolution theory (Ekström et al. and Yang et al. (2018), claiming periodic variability in RSGs 2012) a star in the BSG region could be either coming directly is more robust with a large number of observations and a large from the main sequence to the supergiant region or returning timescale. In our work, the amplitude of the light variation is be- back to higher temperatures before central helium exhaustion, tween 0.2−0.6 ± 0.03 mag over ∼ 100 days. Variability in red after the RSG phase. In order to distinguish whether a source in supergiants has many underlying causes such as radial pulsa- the BSG region is evolving red-ward after the main sequence or tions (Wood et al. 1983; Stothers 1969; Heger et al. 1997) pho- is undergoing a blue-loop, one needs to know about the inter- tospheric changes, huge convection cells (Schwarzschild 1975; nal mixing in the radiative layers, the strength of stellar winds Antia et al. 1984) mass transfer and stellar winds. (if evident) and the metallicity. Variability of BSGs and in par- ticular pulsations of such sources, has been used as a diagnostic tool for the evolutionary stages before and after helium core ig- 4.2. Candidate variable yellow supergiants/hypergiants nition (Ostrowski & Daszynska-Daszkiewicz´ 2015). Kraus et al. Among the massive stars of our sample are 12 variable candi- (2015) studied the blue supergiant 55 Cygnus over a five year date YSGs. The stars show MV brighter than − 5 mag, while the baseline to link its pulsational activity with mass-loss episodes models imply masses and temperatures in the range 15 < M < and the formation of clumps in the stellar wind. 20 M and 5900 < Te f f < 7500 K. They also display a variation To summarize, we identified extragalactic candidate variable in their light curve in both filters within a small timescale. The BSGs, and report their variability over a short base line of ∼ 100 galaxy with the largest number of candidate variable YSGs is days. As BSGs are pre-collapse SN progenitors, large amplitude NGC 1425, which also contains the largest number of candidate variations in their light curves could be indicative of an unstable variable stars. The YSG region is often affected by foreground stage before stellar death. contamination. In our study foreground contamination occurs − between 0.8< V I <1.3 mag. YSGs are among the most visually 4.4. New candidate periodic variables luminous stars, with absolute magnitude MV reaching −9 mag, evolving from the main sequence towards the RSG state, or fol- We conducted a period search to define the periodic variable lowing the opposite path (Humphreys et al. 2016). Another short sources in all three fields (see Table 10). We identified four evolutionary state of post-RSGs with masses between 20−40 Cepheid variables in NGC 1425 within a time-baseline of 100 M , is the yellow hypergiant phase (YHGs) (de Jager 1998). days. We estimated the period of the variable sources based on YHGs display temperatures ranging between 4000−7000 K and their light curve, using the online tool of the NASA Exoplanet 3 log L/Lo > 5.4 and are characterized by atmospheric instability Archive . The periods estimated for the periodic variables range and extended turbulent structures. During the YHG phase, mas- from 25 to 60 days and are marked in Table 7. The periodic vari- sive stars undergo high mass losses shed as expanding pseudo- ables are located in the YSG region between 8 to 9 M near the photospheric shells. Such sources are among the SN type IIn pro- known Cepheids of each field, i.e. the instability strip (Sandage genitors (Smith 2014), which makes their identification and ob- & Tammann 1971; Macri et al. 1999). Their magnitude and color servational follow-up valuable. The brightest source in the YSG ranges are: −4 < MV < −5 mag and 0.5< V−I < 1.2 mag. The region is V1 in NGC 1425 that displays MV ∼ −9 mag, ∼ 30 3 http://exoplanetarchive.ipac.caltech.edu

Article number, page 5 of 28 A&A proofs: manuscript no. aanda light curves of all sources (Fig. 11) show pulsations similar to the massive stars unveiling important information about their prop- Cepheid variables. They are shown as yellow stars in the CMD erties and evolution. in Figure 4. We propose follow-up photometric observations to Acknowledgements. We would like to thank the anonymous referee for the in- better identify the nature of these sources. sightful comments that helped improve this paper. We acknowledge financial support by the European Space Agency (ESA) under the ‘Hubble Catalog of Variables’ program, contract no. 4000112940. This research has made use of 5. Summary the VizieR catalog access tools, CDS, Strasbourg, France and NASA’s Astro- physics Data System (ADS). The Virtual Observatory tools (VO) TOPCAT (Tay- We performed PSF photometry on archival HST WFPC2 im- lor 2005) and Aladin were used for image downloading and table manipulation. ages and created a catalog of luminous stars for the HST Key The data used in this study were downloaded from the Mikulski Archive for project galaxies NGC 1326A, NGC 1425 and NGC 4548. In all Space Telescopes (MAST). All figures in this work were produced using Mat- plotlib a Python library for publication graphics. three fields we studied the massive star population and created three separate sub-catalogs of massive stars with MV < −4.0 mag. In particular the number of massive stars identified in each field were: 5388 in NGC 1326A, 5053 in NGC 1425, and 3783 References in NGC 4548. Using color criteria on the CMD, we separated Anderson, J. & King, I. R. 2000, PASP, 112, 1360 the massive star candidates into three subsets: BSGs, YSGs, and Antia, H. M., Chitre, S. M., & Narasimha, D. 1984, ApJ, 282, 574 RSGs. We calculated the foreground contamination in the direc- Becker, S. A. & Iben, Jr., I. 1980, ApJ, 237, 111 tion of each galaxy using the Besançon Galactic population syn- Bonanos, A. Z. 2007, AJ, 133, 2696 thesis model. The region with the lowest foreground contamina- Brunish, W. M., Gallagher, J. S., & Truran, J. W. 1986, AJ, 91, 598 Cardelli, J. A., Clayton, G. C., & Mathis, J. S. 1989, ApJ, 345, 245 tion in the three galaxies was the BSG region with the percentage Choi, J., Dotter, A., Conroy, C., et al. 2016, ApJ, 823, 102 of foreground stars in that region being: ∼1.3% in NGC 1326A, Conroy, C., Strader, J., van Dokkum, P., et al. 2018, ArXiv e-prints ∼0.8% in NGC 1425, and ∼3.7% in NGC 4548. The region most [arXiv:1804.05860] affected by foreground contamination was the YSG region with de Jager, C. 1998, A&A Rev., 8, 145 ∼25% in NGC 1326A, ∼29% in NGC 1425, and ∼30% in NGC Dohm-Palmer, R. C., Skillman, E. D., Saha, A., et al. 1997, AJ, 114, 2527 Dolphin, A. E. 2000, PASP, 112, 1383 4548 being foreground stars. Eggenberger, P., Meynet, G., & Maeder, A. 2002, A&A, 386, 576 We calculated the de-projected distances of the massive stars Ekström, S., Georgy, C., Eggenberger, P., et al. 2012, A&A, 537, A146 and estimated the blue to red supergiant ratio at various radial Freedman, W. L., Madore, B. F., Gibson, B. K., et al. 2001, ApJ, 553, 47 distances for the three galaxies. The B/R ratio decreases mono- Graham, J. A., Ferrarese, L., Freedman, W. L., et al. 1999, ApJ, 516, 626 Grammer, S. & Humphreys, R. M. 2013, AJ, 146, 114 tonically with increasing distance and decreasing metallicity. We Groenewegen, M. A. T. & Sloan, G. C. 2018, A&A, 609, A114 examined the recent star formation history of the field over the Heger, A., Jeannin, L., Langer, N., & Baraffe, I. 1997, A&A, 327, 224 last 100 Myrs within the WFPC2 field of view. We derived the Heger, A. & Langer, N. 2000, ApJ, 544, 1016 luminosity function based on the blue HeB stars and estimated Humphreys, R. M. & Davidson, K. 1979, ApJ, 232, 409 the SFR using the Salpeter slope for the IMF. NGC 4548 in- Humphreys, R. M., Martin, J. C., Gordon, M. S., & Jones, T. J. 2016, ApJ, 826, 191 cludes the largest number of stars and has the highest star for- Humphreys, R. M. & Sandage, A. 1980, ApJS, 44, 319 mation rate compared to NGC 1326A and NGC 1425. The star Kalari, V. M., Vink, J. S., Dufton, P. L., & Fraser, M. 2018, A&A, 618, A17 formation history of NGC 1326A shows an increase indicating Kochanek, C. S., Fraser, M., Adams, S. M., et al. 2017, MNRAS, 467, 3347 high star formation rates over the past 70 Myrs, while in NGC Kourniotis, M., Bonanos, A. Z., Yuan, W., et al. 2017, A&A, 601, A76 Kraus, M., Haucke, M., Cidale, L. S., et al. 2015, A&A, 581, A75 1425 the star formation history has a recent peak at ∼ 10 Myrs, Langer, N. 2012, ARA&A, 50, 107 an indication of a star formation event. Langer, N. & Maeder, A. 1995, A&A, 295, 685 We conducted a variability search among 5789 sources in Levesque, E. M., Massey, P., Olsen, K. A. G., et al. 2006, ApJ, 645, 1102 NGC 1326A, 5232 sources in NGC 1425, and 5790 sources in Lianou, S. & Cole, A. A. 2013, A&A, 549, A47 NGC 4548 using three different methods: the MAD, IQR, and Macri, L. M., Huchra, J. P., Stetson, P. B., et al. 1999, ApJ, 521, 155 Maeder, A., Lequeux, J., & Azzopardi, M. 1980, A&A, 90, L17 the inverse von Neumann ratio. The number of stars used for Maeder, A. & Meynet, G. 2000, A&A, 361, 159 the variability search include all sources that fulfilled the quality Massey, P. 2003, ARA&A, 41, 15 criteria mentioned in Section 2.2. The number of stars in Table 5 Moriya, T. J. 2018, MNRAS, 475, L49 imply to the massive stars in each field. The variability search Mould, J. R., Huchra, J. P., Freedman, W. L., et al. 2000, ApJ, 545, 547 Ostrowski, J. & Daszynska-Daszkiewicz,´ J. 2015, MNRAS, 447, 2378 yielded 243 new variable sources in addition to the 87 known Percy, J. R. & Kim, R. Y. H. 2014, Journal of the American Association of Vari- Cepheid variables in the three galaxies. We used the MESA mod- able Star Observers (JAAVSO), 42, 267 els and evolutionary tracks to model our results and classify the Prieto, J. L., Stanek, K. Z., Kochanek, C. S., et al. 2008, ApJ, 673, L59 new variable candidates. Among the luminous massive variable Prosser, C. F., Kennicutt, Jr., R. C., Bresolin, F., et al. 1999, ApJ, 525, 80 sources are 138 variable candidate BSGs, 86 variable candidate Robin, A. C., Reylé, C., Derrière, S., & Picaud, S. 2003, A&A, 409, 523 Sandage, A. & Tammann, G. A. 1971, ApJ, 167, 293 YSGs, and 19 variable candidate RSGs. In addition to the can- Schwarzschild, M. 1975, ApJ, 195, 137 didate variable massive stars we identified four periodic variable Smith, N. 2014, ARA&A, 52, 487 candidates in NGC 1425, which we suggest for follow-up obser- Sokolovsky, K. V., Gavras, P., Karampelas, A., et al. 2017, MNRAS, 464, 274 vations. Soraisam, M. D., Gilfanov, M., Kupfer, T., et al. 2018, A&A, 615, A152 Spetsieri, Z. T., Bonanos, A. Z., Kourniotis, M., et al. 2018, A&A, 618, A185 This work provides a census of the massive star population Stothers, R. 1969, ApJ, 156, 541 and variable massive stars in three HST Key Project galaxies us- Szczygieł, D. M., Stanek, K. Z., Bonanos, A. Z., et al. 2010, AJ, 140, 14 ing archival data from the Hubble Legacy Archive (HLA). Future Taylor, M. B. 2005, in Astronomical Society of the Pacific Conference Se- work on the massive star population in distant fields using the ries, Vol. 347, Astronomical Data Analysis Software and Systems XIV, ed. combination of deep HST data and high-precision PSF photom- P. Shopbell, M. Britton, & R. Ebert, 29 Whitmore, B. C., Allam, S. S., Budavári, T., et al. 2016, AJ, 151, 134 etry, will shed light on the link of massive stars with the galactic Wood, P. R., Bessell, M. S., & Fox, M. W. 1983, ApJ, 272, 99 star formation history. Increasing the number of photometric and Yang, M., Bonanos, A. Z., Jiang, B.-W., et al. 2018, A&A, 616, A175 spectroscopic observations of massive stars could help identify Yang, M. & Jiang, B. W. 2012, ApJ, 754, 35 SN Type II progenitors and constrain the evolutionary models of

Article number, page 6 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

Table 1. Catalog of 5897 stars in NGC 1326A.

ID RA (J2000) Dec (J2000) X (pixels) Y(pixels) (mag) σ (mag) (mag) σ (mag) 1 3:25:03.205 -36:21:57.02 88.87 490.39 24.539 0.010 22.788 0.008 2 3:25:03.591 -36:22:01.12 68.74 355.53 23.924 0.008 23.905 0.013 3 3:25:03.154 -36:21:54.00 56.39 549.66 27.395 0.077 23.164 0.011 4 3:25:03.005 -36:22:06.73 266.77 361.29 24.659 0.008 24.654 0.002 5 3:25:02.120 -36:21:59.13 338.64 640.10 25.348 0.016 23.865 0.015 6 3:25:01.619 -36:22:22.16 766.54 338.78 25.764 0.017 23.930 0.012 7 3:25:03.805 -36:22:12.63 188.22 125.41 25.168 0.012 25.458 0.039 8 3:25:01.933 -36:22:04.16 447.80 587.63 25.414 0.014 25.467 0.040 9 3:25:03.533 -36:22:17.63 314.34 87.91 25.913 0.019 24.266 0.016 10 3:25:03.570 -36:22:00.98 71.06 361.40 25.504 0.017 25.695 0.053 Note. – Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcsec- onds. This table is available in its entirety in an electronic version. The ten first entries are shown as guidance for the content of the tables.Units of X and Y are pixels coordinates.

Table 2. Catalog of 5232 stars in NGC 1425.

ID RA (J2000) Dec (J2000) X (pixels) Y (pixels) (mag) σ (mag) (mag) σ (mag) 1 3:42:15.534 -29:54:51.60 607.53 672.60 22.677 0.004 22.341 0.005 2 3:42:17.574 -29:55:05.22 303.50 92.98 23.386 0.004 22.939 0.007 3 3:42:16.400 -29:54:48.58 367.20 584.80 23.513 0.005 22.702 0.007 4 3:42:15.199 -29:54:52.36 695.40 714.03 23.715 0.005 22.933 0.007 5 3:42:16.777 -29:55:06.89 510.48 193.74 23.664 0.005 23.495 0.009 6 3:42:17.543 -29:54:56.66 202.43 251.88 24.152 0.007 23.758 0.013 7 3:42:16.751 -29:55:00.70 438.47 309.33 24.300 0.007 23.418 0.010 8 3:42:16.720 -29:54:57.16 400.82 377.97 25.471 0.019 23.111 0.007 9 3:42:15.594 -29:54:51.75 595.27 660.14 24.100 0.010 24.123 0.018 10 3:42:15.771 -29:54:56.63 615.72 543.30 25.451 0.020 23.219 0.008 Note. – Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcsec- onds. This table is available in its entirety in an electronic version. The ten first entries are shown as guidance for the content of the tables.

Table 3. Catalog of 5790 stars in NGC 4548.

ID RA (J2000) Dec (J2000) X (pixels) Y (pixels) (mag) σ (mag) (mag) σ (mag) 1 3:25:03.205 -36:21:57.02 88.87 490.39 24.539 0.009 22.788 0.008 2 3:25:03.591 -36:22:01.12 68.74 355.53 23.924 0.007 23.905 0.013 3 3:25:03.154 -36:21:54.00 56.39 549.66 27.395 0.074 23.164 0.011 4 3:25:03.005 -36:22:06.73 266.77 361.29 24.659 0.008 24.654 0.020 5 3:25:02.120 -36:21:59.13 338.64 640.10 25.348 0.017 23.865 0.014 6 3:25:01.619 -36:22:22.16 766.54 338.78 25.764 0.020 23.930 0.014 7 3:25:03.805 -36:22:12.63 188.22 125.41 25.168 0.011 25.458 0.036 8 3:25:01.933 -36:22:04.16 447.80 587.63 25.414 0.020 25.467 0.015 9 3:25:03.533 -36:22:17.63 314.34 87.91 25.913 0.014 24.266 0.041 10 3:25:03.570 -36:22:00.98 71.06 361.40 25.504 0.015 25.695 0.053 Note. – Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcsec- onds. This table is available in its entirety in an electronic version. The ten first entries are shown as guidance for the content of the tables.

Table 4. Properties of NGC 1326A, NGC1425 and NGC 4548.

Galaxy i D0 µ0 Z Morphological type Redshift Absolute Magnitude (deg) (Mpc) (mag) (dex) z (mag) NGC 1326A 50 16.1 ±0.04 31.04 ±0.002 8.50 Sb 0.006108 −18.0 ±0.13 NGC 1425 77 21.8 ±0.08 31.70 ±0.200 9.00 Sb 0.005037 −21.9 ±0.10 NGC 4548 35 16.2 ±0.50 31.05±0.080 9.34 Sb 0.001621 −22.3 ±0.61

Note. – Values of inclination (i), distance (D), distance modulus (µ 0) and metallicity (Z), redshift, morphological type and absolute magnitude are from the study of Freedman et al. (2001) and https://cdsportal. u-strasbg.fr.

Article number, page 7 of 28 A&A proofs: manuscript no. aanda

Table 5. Massive star population in NGC 1326A, NGC1425 and NGC 4548.

Galaxy #Stars #BSGs #variable BSGs #YSGs #variable YSGs #RSGs #variable RSGs NGC 1326A 5388 (8.0%) 2652 (1.0%) 21 868 (25.0%) 22 1868 (10.6%) 5 NGC 1425 5053 (10.0%) 2833 (0.8%) 53 939 (29.0%) 41 1281 (17.0%) 8 NGC 4548 3783 (11.0%) 2155 (3.7%) 64 507 (30.0%) 23 1121 (3.21%) 6 Total 16811 7640 138 2314 85 4270 19 Note. – The percentages next to columns 1−7, indicate the percentage of foreground contamination in the corresponding popu- lation.

Article number, page 8 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548 I ∆ and V ∆ I HSC MatchID Notes ∆ V ∆ I , V η / 1 I IQR V IQR I MAD V MAD I σ I V σ –Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcseconds. Numbers 1 or 0 in columns MAD, IQR (J2000) (J2000) (pixels) (pixels) (mag) (mag) (mag) (mag) (mag) (mag) Properties of the variable candidates in NGC 1326A ordered by average magnitudes. For convenience we use the letter "V" to name each variable in this field. Note. and inverse von Neumann ratioshow the show amplitude whether of the variability. star was characterized as a variable in the respective index. Units of X and Y are pixels coordinates. Columns IDV1V2 RA 3:25:12.065V3 3:25:03.610 -36:22:23.02V4 3:25:07.386 -36:22:01.14V5 662.8 3:25:07.578 -36:21:40.45V6 68.74 Dec 3:25:10.705 -36:21:55.72 743.68 506.12V7 3:25:09.799 -36:21:52.99 355.53 426.93 23.378V8 60.04 3:25:06.806 -36:21:58.66 731.98 23.924V9 0.004 181.9 3:25:07.950 -36:21:53.24 608.12 24.016V10 0.008 X 404.25 22.47 3:25:07.029 -36:22:13.76 367.55V11 0.009 3:25:08.102 23.905 357.28 24.1 24.104 -36:21:46.15 0.005 365.24V12 3:25:03.026 -36:21:58.96 24.239 0.013 24.266 99.03 0.006 436.12 0.007V13 3:25:07.410 -36:22:06.69 360.44 0.018 Y 0.008 454.4 23.972 24.269V14 1 3:25:08.504 24.075 -36:21:23.83 266.77 24.322 63.09 1 24.358 0.013V15 0.008 3:25:08.771 -36:21:27.26 248.09 0.015 172.48 1 0.007 361.29 24.412 0.019V16 3:25:01.644 -36:22:39.17 24.175 24.514 V 57.23 23.336 609.38 24.659V17 0.008 3:25:12.860 1 -36:22:22.11 1 0.017 252.25 1 0.008 1 0.008 24.831V18 3:25:08.418 1 0.008 -36:22:16.25 24.007 689.89 766.54 0 22.689 606.32V19 3:25:07.017 -36:21:10.11 24.654 0.014 0.01 782.54 24.921 1 338.78 0.006 25.323V20 1 3:25:10.567 1 -36:21:54.42 1 200.05 0.011 1 1 0.02 22.984 754.69 25.764V21 03:25:03.95 0.018 -36:21:45.34 1 382.63 1 1 23.811 792.88 0.006 25.847V22 3:25:10.396 1 0.017 -36:22:25.92 24.452 768.89 1 1 0.012 25.885 126.3V23 3:25:11.189 1 0.027 1 -36:22:07.09 1 23.930 1 124.52 0.023 1 333.98V24 3:25:08.800 1 1 -36:22:17.08 25.156 1 0.02 667.28 25.956 0.012 1 181.62 26.039V25 3:25:03.257 1 -36:21:48.59 1 621.13 0.033 1 0.028 0 0 25.133 1 26.141 544.7V26 1 3:25:12.079 0.024 1 -36:21:30.63 1 1 586.72 1 627.76 1 0.031 25.04V27 0 3:25:08.078 -36:22:25.40 1 25.378 0.03 448.95 26.182 1 0 223.21 26.295V28 1.0 3:25:12.363 0 -36:21:51.65 1 1 0.033 651.41 0.042 0.2 0.024 0 25.211 182.82 0 1 26.465 1V29 3:25:09.870 1 0.028 1 -36:22:14.59 499.75 0.2 0 24.312 771.25 1 0.039 26.501V30 3:25:07.342 0.043 0.3 1 -36:21:44.19 25.609 1 747.67 1 1 0.2 190.01 1 1 0.015 26.521V31 0 3:25:08.432 0.5 0.036 1 -36:22:01.93 26.041 0.047 0.8 717.8 0 0.2 1 697.66 1 26.522V32 3:25:03.430 0.1 0 0.032 -36:21:49.18 1 25.541 100711291 365.33 0.104 1 1V33 0 3:25:10.554 21471881 1 0.048 -36:22:01.00 26.63 271.42 0.1 25.892 548.75 0.4 0.2 1 0.06 1 0 0 218.62 0 1V34 candidate 3:25:11.556 0.3 51171750 -36:22:35.97 0.3 YSG 26.185 0 26.664 0.056 0.037 103.3 0 1 198.86 26.684V35 3:25:06.693 0 -36:21:59.34 0 458.04 1 0.099 0.4 0.045 1 0.2 26.075 26.705V36 candidate 3:25:04.707 0.8 1 0.045 -36:21:26.83 0.3 BSG 1 771.17 1 389.2 1 0 1 1 26.209 702.58 1 0.071V37 3:25:06.615 0.7 0.061 1 -36:21:28.13 26.374 205.93 1 0.2 517.85 1 1 0.097 26.733V38 3:25:07.951 1.0 26.71 1 0 -36:21:28.50 0.1 25.439 352.99 0.114 20795427 524.64 26.739V39 3:25:08.459 0.3 1 0.038 1 0 -36:22:01.13 0.3 1 0 196.58 0 0.063 0.036 1.2 1 327.51 1 26.781V40 3:25:06.465 1 0.042 -36:21:23.01 0.2 26.229 426.33 0 1.0 25.616 1 1 515.31 1 0 26.838V41 3:25:06.931 0.038 -36:20:54.33 0.3 candidate 21211 0.079 BSG 26.14 candidate 96.63 0.8 0 252.91 0.5 0.048 BSG 1 26.845V42 1 3:25:04.678 0.041 1 0 -36:21:26.58 candidate 0 26.221 472.02 1 BSG 37669517 1 0.3 0.075 26.943V43 3:25:03.167 0.2 -36:21:23.05 712.02 0 25.975 0.04 197.36 1 0.068 0 59943606 1 candidate 1 716.92 0.6 1 BSG candidateV44 1 3:25:03.167 0.057 -36:22:06.92 RSG 57563267 400.36 26.951 0.058 1.0 candidate 0 1.0 26.613 546.34 RSG 1 1 26.959V45 3:25:08.145 1 0 1 -36:22:06.92 18558392 0.5 25.935 1 0.051 64.05 1 358.78 0.102 27.023V46 3:25:03.829 1.0 0.043 1 1 -36:22:11.45 1 241.1 0.08 1 0.5 1 26.301 1.0 0 27.061V47 3:25:07.091 0.6 0.045 -36:22:21.71 0 134.93 25.856 447.81 1 0.3 0 1 0.085V48 3:25:03.320 0 0.052 1 -36:21:16.73 0.6 1 26.462 199.76 27.111 333.8 0.047 0.8 459.36 1 0 3:25:05.855 1 0 -36:22:00.80 0.4 26.125 376.76 1 0.056 0.09 1 109.74 0.5 0 27.244 27.263 1 0.6 1 -36:21:19.77 122.09 1 0.079 0 0.1 0 26.628 344.07 0.8 0.053 0.063 1 1 324.31 27.3 1 0.7 69513998 0 411.43 0.106 27.327 0 1 25.895 0.5 0 1 26.94 1 1 488.78 0 0.8 27.337 0.059 0.2 0.058 0 0 0.053 candidate 0.9 RSG 1 0 27.443 0.4 0.14 0 0.063 0 26.283 0 26.78 0.3 0.062 1 0 85805459 0.6 1 0 0.071 26.57 0 1 0.8 0 0.12 1 86993890 0.8 26.752 1 1 0 1.2 1 0.109 0 1 0.119 1.2 0 0.6 0 1.2 1 0 0 1 1 0 1.2 1 10543145 1 0 1.2 1 0 1.2 1.2 0 0 1.0 1 1 1.0 0 0 0 1 1.2 0.8 1 0 2433197 1 1.2 0 1 0.8 0 1 0.8 1 0.8 1 0 0.8 1 58705971 0.4 0 0 1 1.2 0.3 1 0.8 0.6 0 1 11471347 1 0 1.2 0.7 0 56314445 0.6 1 1.5 1 0.8 1.2 1 0 90123409 0.8 1.4 0.6 1.2 0.8 1.2 0.6 0.6 0.6 1 53129508 82802949 93149850 Table 6.

Article number, page 9 of 28 A&A proofs: manuscript no. aanda I ∆ and V ∆ I HSC MatchID Notes ∆ V ∆ I , V η / 1 I IQR V IQR I MAD V MAD I σ I V σ – Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcseconds. Numbers 1 or 0 in columns MAD, IQR (J2000) (J2000) (pixels) (pixels) (mag) (mag) (mag) (mag) (mag) (mag) Properties of the variable candidates in NGC 1425 ordered by average magnitudes. For convenience we use the letter "V" to name each variable in this field. Note. and inverse von Neumann ratioshow the show amplitude whether of the variability. star was characterized as a variable in the respective index. Units of X and Y are pixels coordinates. Columns IDV1V2 RA 3:42:15.539V3 3:42:20.029 -29:54:51.62V4 3:42:18.351 -29:54:47.57 607.53V5 3:42:19.469 -29:53:59.39 288.98V6 672.6 Dec 3:42:18.570 -29:53:42.77 547.65V7 72.49 3:42:22.972 -29:54:54.44 596.66 22.662V8 376.16 3:42:16.946 -29:55:10.64 23.381V9 0.004 78.41 402.37 23.581 3:42:17.970 -29:53:56.02V10 0.005 469.5 22.323 X 23.605 3:42:20.380 0.005 -29:54:48.04 72.46V11 679.1 3:42:18.356 22.839 0.005 0.005 -29:54:53.31 22.991 175.09 485.1V12 3:42:23.636 -29:53:58.01 23.722 0.008 256.56 23.022 292.63 0.007V13 3:42:17.749 -29:55:02.87 23.935 548.53 Y 59.46 0.005 1 23.968 0.007V14 3:42:20.302 -29:54:52.61 146.83 585.08 0.005 1 23.237 24.019 376.8V15 0.006 3:42:19.723 1 -29:54:42.75 24.053 79.59 471.66 0.008 23.51V16 0.009 3:42:15.877 1 -29:54:39.85 23.931 345.69 24.062 V 0.006 0 24.232V17 3:42:17.557 -29:54:04.96 23.014 282.61 0.009 0.015 0.006 107.7 1 23.787 54.01V18 1 3:42:15.719 0.006 -29:55:06.01 1 692.26 24.275 0.01 23.101 0.011V19 3:42:21.999 -29:54:04.63 294.22 1 23.677 316.94 24.276 1 1 0.008 1 0.008 78.84V20 3:42:16.721 -29:55:25.97 707.22 24.305 0.008 1 0.01 24.078 71.03V21 1 3:42:15.025 1 1 -29:54:59.73 1 24.823 0.007 276.1 23.657 0.016 63.73V22 3:42:17.621 1 1 -29:54:51.11 0 25.057 0.016 431.0 0 1 24.014 0.012V23 3:42:16.262 1 -29:54:53.79 1 734.87 25.162 597.5 0.014 24.695 1 0.014V24 1 3:42:15.596 1 -29:54:04.50 0 326.95 1 125.44 0.027 768.76 1 25.179 0.032 24.91V25 1 3:42:20.106 1 -29:54:03.99 0 666.15 25.226 1 1 24.875 282.59 25.252V26 0.011 1 3:42:17.018 1 -29:53:59.76 1 0.031 722.16 0.012 1 123.03 1 25.289V27 1 3:42:16.301 0.04 1 0.017 0 -29:54:37.00 24.572 1 0.12 407.59 1 25.226 25.346V28 3:42:14.909 0.013 1 -29:54:48.17 54.1 1 1 24.558 1 0.018 0.2 1 51.99 570.31 0.035V29 3:42:15.821 0.2 0.019 0 -29:54:51.69 0.2 1 24.708 362.69 0.029 1 1 0 1 25.347 25.403V30 3:42:15.629 0.1 1 -29:54:06.59 686.92 1 25.534 768.39 0.024 1 0.2 600.18 1 1V31 0.029 0 3:42:16.726 1 0.016 1 -29:54:52.45 0.1 683.16 25.412 0.057 1 1 782.04 0 25.416V32 0.2 3:42:17.595 1 -29:54:57.24 24.908 0.2 23.125 589.29 1 0.024 0 0 1 1 25.436 63.23V33 3:42:17.272 90652043 0.014 1 -29:55:06.13 0.045 400.82 0.007 0.1 0.3 0 1 1 25.424 650.79 1 9637663V34 3:42:18.872 0.2 -29:54:34.70 1 25.216 0.02 310.97 25.447 1 1 41675618 377.97 1 1 0.065 25.484V35 0.3 candidate 3:42:15.772 0.2 -29:54:09.60 YSG 341.29 0.037 1 0.028 0.3 1 1 1 0.3 24.718 1 1 25.502V36 candidate 3:42:18.782 0.1 0.016 -29:54:03.34 68.1 YSG candidate 1 424.6 0 24.829 7739340 YSG 0 0.028 53.92V37 3:42:16.020 0.1 1 0.019 0.3 1 -29:55:30.24 0.2 25.025 1 713.67 0 1 1 25.591 0.051V38 58838018 3:42:15.732 0.6 19102580 -29:54:09.67 0.6 23.106 1 25.606 371.7 0.037 328.4 1 0 0 1 candidateV39 0.019 3:42:16.012 0.3 0 YSG -29:54:05.62 77.0 0.3 1 642.41 0.007 68385761 0.022 65467227 1 1 25.665 candidateV40 candidate 1 3:42:15.690 0.2 1 YSG -29:54:09.42 25.246 170.58 0.5 BSG 0 698.08 1 20177712 0 25.878 1 25.687V41 0.018 0 3:42:19.711 0.4 -29:54:05.88 66.7 0.2 0.041 645.04 1 25.718 candidate candidate 0 20606278 1 1 YSG YSG 0.074 59.29V42 0.026 0 3:42:22.870 -29:54:35.47 24.633 0.7 1 699.16 0 0.4 candidate 0.018 1 95116497 YSG 25.775 67.31V43 3:42:15.667 1 0 -29:55:36.10 25.859 0.4 0 0.023 149.28 25.791 0.4 candidate 1 90537371 1 24.734 YSG 1 53.21V44 0.028 3:42:17.636 1 1 -29:54:02.82 0 0.096 296.42 1 25.945 0.3 0.034 candidate 36741455 0.7 309.16 BSG 1 0.022V45 3:42:18.911 0.3 0 1 -29:55:05.68 25.497 726.22 25.949 candidate 1 0.036 0.3 73522719 0.8 25.294 YSG 0 25.951 690.0V46 3:42:19.012 0 -29:54:19.81 0.063 294.38 1 candidate 1 0.043 0.3 0.2 0 1 25.329 YSG 0.072 68.72V47 0 3:42:15.505 37383109 1 0.023 1 -29:54:51.80 0.6 0 338.36 25.998 0.3 1 25.346 0.4 1 0.052 73.19V48 3:42:15.818 -29:54:01.83 25.266 26.012 500234 1 0.021 64.66 1 1 316.11 0.3 0 107344064 0.072V49 3:42:19.524 1 1 -29:54:03.74 746.99 0 26.022 0.036 0.3 0.035 1 0.4 45871608 1 0.6 25.15 26.276V50 3:42:18.878 1 0 -29:55:04.43 45578344 135.92 1 1 0.026 706.8 0 25.368 56.93 3:42:17.618 0.6 0 0.041 -29:53:56.81 52701106 0.029 137.06 26.324 1 1 0.3 1 0.4 0 26.189 0.8 0.064 0 -29:55:02.63 16420841 0 26.173 1 539.26 26.349 79.67 0.034 1 176.73 0 0.084 0.4 1 0 0.5 1 238.44 0.129 1 0.052 25.029 434.64 0.6 26.402 26.417 0.3 40931113 1 83509791 1 1 1 0.4 25.424 1 0.037 26.446 125.9 0.052 1 1 0.033 0 0.3 1 0 0.6 85512615 1 1 0.072 0.034 candidate 1 25.472 92064031 0.5 25.878 RSG 26.458 1 0.6 1 1 0 1 25.802 0 0.067 0.062 0.5 0.031 62147934 1 0.7 0 0 0.5 1 1 0.057 1 25.973 0 1 100312212 0.5 1 1 1 0.9 0 0.066 0 1 0.5 0 1 0.6 0 1 0.6 1 0 1 0.6 0 51633672 1 1 0.6 0 0.4 0 1 1 9181183 0.9 1 1 0.4 1 1 0.8 74867700 0 0 0.5 0 0.3 0.5 0 1 0 0.3 86921818 1 candidate 0 RSG 0.9 0 1 0 0 0.3 0.6 63484288 0.8 0.6 1 0 1 0 0.6 1 0 0.5 63484288 0.5 0.6 0 0 0.6 0 0.6 0.6 0.6 99010888 0 52737352 0.6 0.6 0 0.8 22885126 0.9 1.2 57959110 0.8 1.2 0.2 70111043 0.6 20780705 91641235 0.5 73383575 Table 7.

Article number, page 10 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548 I ∆ 50 days) 29 days) 29 days) 60 days) 42 days) = = = = = and V ∆ I HSC MatchID Notes ∆ V ∆ I , V η / 1 I IQR V IQR I MAD V MAD I σ I V σ (J2000) (J2000) (pixels) (pixels) (mag) (mag) (mag) (mag) (mag) (mag) – Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcseconds. Numbers 1 or 0 in columns MAD, IQR Table 7 continued. Note. and inverse von Neumann ratioshow the show amplitude whether of the variability. star was characterized as a variable in the respective index. Units of X and Y are pixels coordinates. Columns IDV51V52 3:42:15.955 RAV53 3:42:15.373 -29:54:05.15V54 3:42:19.577 -29:53:59.48 684.61V55 3:42:16.216 -29:54:37.80 776.83V56 3:42:16.005 86.25 -29:54:40.69 Dec 144.27V57 3:42:16.250 56.28 -29:54:53.00 303.37 26.533 3:42:23.221 285.7 -29:53:56.30 515.36 26.535 0.049 768.7 -29:54:57.96 741.44 26.551 0.055 26.138 570.3 X 26.569 569.9 0.038 25.866 0.114 168.6 26.621 0.038 25.931 0.109 26.627 400.4 0.035 26.439 0.065 1 Y 0.046 26.018 26.635 0.107 1 25.762 0.066 0.035 1 0.07 1 25.703 1 V 1 1 0.046 0 1 1 0 1 1 0 1 1 0 1 1 1 1 0 1 0 0 1 0 0 1 0.5 0 1 0.8 0 1 0.4 0.5 0 0.4 0.7 0 0.8 0.5 3333322 0.6 0.8 0.9 1.0 0.5 0.9 79220173 candidate periodic variable (P V58V59 3:42:20.149V60 3:42:17.378 -29:54:33.33V61 3:42:16.481 -29:54:45.94V62 125.6 3:42:19.765 -29:55:00.84V63 56.3 3:42:17.026 -29:54:36.86 503.19V64 373.7 3:42:17.550 -29:54:58.47 122.72V65 351.06 26.675 462.0 3:42:17.401 -29:55:49.95 363.29V66 302.24 3:42:20.538 26.717 -29:55:00.00 0.039 397.92 26.693V67 287.41 3:42:16.005 26.722 -29:55:18.40 0.039 26.796 285.91V68 0.047 414.84 3:42:15.551 26.733 -29:54:51.58 0.046 25.399 154.16 0.129V69 26.397 202.02 3:42:16.194 -29:54:46.35 26.75 471.15V70 0.04 0.041 26.43 361.87 0.123 3:42:19.922 26.754 -29:54:48.81 533.22V71 1 0.039 25.911 558.42 3:42:20.176 26.777 -29:54:39.02 0.11 0.038 400.48V72 1 25.205 746.67 0.061 3:42:18.563 26.786 -29:55:05.26 1 26.393V73 0.04 92.26 599.78 3:42:19.199 26.909 -29:55:35.54 0.03 0.046 192.59V74 0.093 1 1 3:42:21.380 25.97 26.917 -29:53:38.50 1 0.054 310.95 26.336 369.78V75 237.09 0 3:42:17.137 -29:54:06.84 0.058 0 26.674 642.29 0.061V76 26.931 0.094 1 1 328.29 3:42:24.036 26.932 -29:54:24.72 25.679 230.86V77 0.146 0.054 1 1 604.24 3:42:16.328 26.995 -29:54:46.47 466.385 0.046 1V78 0.062 1 0 0 26.543 685.52 3:42:17.463 27.008 -29:55:12.83 0 0.048 26.167 760.46V79 46.96 1 0 1 0.116 3:42:16.474 27.029 -29:54:46.40 0.057 26.224 672.69 1V80 0.072 1 0 392.97 3:42:16.735 27.032 -29:54:59.58 0.053 0 26.111V81 0 0.073 58.81 0 0 0 3:42:19.627 27.048 89.74 -29:55:08.41 1 0.058 26.511 498.47V82 0.088 1 1 1 0 3:42:16.291 -29:54:35.76 0 0.052 458.61 26.571 540.07 1V83 27.073 0.11 1 378.83 0 0 3:42:18.981 -29:54:39.87 1 26.923 153.35V84 27.074 0.133 0 0.052 1 0 1 172.78 3:42:15.673 27.079 -29:55:03.33 0 287.02 0V85 1 0.131 1.2 0.055 1 26.891 298.56 0 3:42:19.563 27.082 -29:54:57.54 0 1V86 0.05 84.54 0 1.2 1 1 781.71 1 0.154 3:42:17.915 26.69 27.084 -29:54:45.77 0.5 0.052 650.81 0V87 0 1 0.5 0 3:42:20.141 26.66 27.085 -29:55:02.81 0 0.058 0 1 122.62 26.755 0.164V88 1 75.79 0.6 1 543.61 0.6 3:42:22.508 -29:54:02.37 1.2 0 0.058 0.5 1 199.54 0.124V89 1 27.097 0.148 1 26.3 1 3:42:15.388 27.099 -29:55:37.02 0 84479115 0 232.78 26.773 366.41V90 0.8 1 0.057 0.8 0.5 1 0 0 3:42:17.130 -29:54:49.37 0.056 0 75007472 78.3 0.8V91 0 27.116 254.6 0.09 1 0.14 1 26.113 567.74 3:42:20.369 -29:53:47.30 1 0 1 26.947 607.68V92 1 1.5 1.2 0.7 0 1.1 0.06 27.121 0.077 3:42:17.558 27.124 -29:55:25.90 85716829 663.74 742.54V93 0 0.166 1 0.8 73155751 1 1 727.97 3:42:24.786 -29:54:47.12 1 0.056 0 0.054 0 26.005V94 27.124 92.12 0.9 1.2 1 1.2 1 1 3:42:17.589 27.143 322.8 -29:55:29.20 1 1 0 25.877 26.226 0.072V95 0 67.77 0.066 1 0.6 3:42:18.051 -29:54:08.30 0.9 0.057 0 410.64 552.78 0.061V96 0 27.146 0.084 1 1.2 27.033 0.8 3:42:15.810 -29:54:57.42 1 424.13 1 26.406 533.02V97 1612324 27.161 1 0.067 1 0 1.2 1 781.16 1 0.181 3:42:19.226 -29:55:05.01 0 0.6 1V98 27.167 0.113 69.18 1 0.056 0.8 1 25.759 243.01 0.8 1 3:42:16.448 27.175 -29:55:02.94 1 714.27 1V99 0.055 25.571 0.8 0.061 3:42:16.256 27.181 -29:55:20.24 1 0.9 1 0.054 0 112.49 1V100 0 146.2 0 0.9 94862026 1 0 27.103 candidate 1.2 0.041 3:42:17.302 periodic 383.1 -29:54:56.89 0.063 1 variable 26.962V101 (P 3:42:17.121 72.06 1.2 1 1 137.05 0 27.187 -29:54:48.13 0 0.18 0 45614411 0.8 25.955V102 27.197 0.129 3:42:16.660 -29:55:04.67 493.4 candidate 1 1.2 1 periodic 27.198 0.057 0 0.9 variable 0 0 97364472 0 106.73 (P 359.9 0.066 3:42:17.010 -29:55:00.14 0.061 1 1.2 0 392.81 0 candidate 26.601 444.97 periodic 0.07 1 103267462 -29:54:52.01 1.0 variable 0 1 0 0 26.469 451.16 (P 461.21 27.212 candidate 0.8 1 181.35 RSG 7043734 27.238 1 0.9 0.14 0 0.9 0 259.73 0.106 25.03 27.293 0.059 0 17813499 1 0 27.387 336.5 0.059 0 0 1 0.067 0 27.245 435.11 1 0.029 0 0.064 0.7 1 26.231 0.8 1 3845446 27.407 1.2 1 0.9 1 0 25.992 0.186 27.422 1 26.616 0 0.081 0 0.8 0.067 0 0 0.072 1 0.5 0.066 0.107 0 1.2 0 0.8 26.14 1 1 0 26.334 1 1 0 0.9 0 0.9 0 1 0 0.3 1 0.087 0 0.09 1 0.6 1.2 1 1 1 0 83539125 0.2 0 1 1.0 1 1 80153594 0 1 0 0.8 1 0.3 1.2 0 candidate 0 periodic 1 variable (P 0 0.8 16527370 1 1.0 1 0 0.3 0 1.2 57938375 1 0 29608543 1 0 0 0.9 1 1 1.0 1.2 0.6 0 0 0 0.9 0 1 0 34302839 0.3 1 1.2 0 1 27428939 0.6 0.2 1 0.5 0 1 1 0 0.4 0 0.0 0.0 1.2 1.1 0 1.0 0.7 0 1.2 1.2 candidate 1.1 RSG 0.5 101548221 candidate 0.6 0.6 RSG 1.2 87402582 39509540 11666137 1.1 24815704 0.0 48554067 candidate RSG Table 8.

Article number, page 11 of 28 A&A proofs: manuscript no. aanda I ∆ and V ∆ I HSC MatchID Notes ∆ V ∆ I , V η / 1 I IQR V IQR I MAD V MAD I σ I V σ 14:29:02.3214:28:44.86 615.0714:28:26.29 740.39 508.5114:29:17.79 761.15 350.4614:29:03.65 23.13 783.82 162.91 23.38514:28:24.83 137.36 0.005 701.88 23.445 0.00514:28:23.57 580.28 22.554 412.85 23.491 0.00614:28:34.28 23.367 768.82 108.85 0.007 23.527 0.00714:29:08.27 23.396 746.26 0.011 135.72 23.558 0.00614:29:04.23 23.027 203.58 0.012 243.11 23.564 1 0.00514:29:27.33 23.254 529.68 0.013 1 474.39 23.654 0.00714:28:38.22 23.277 403.75 0.013 1 510.46 23.657 0.00614:29:24.51 23.916 315.33 0.01 1 498.11 23.675 0.00914:28:25.77 1 23.778 0.016 70.65 1 697.37 1 23.731 0.00614:29:10.34 24.418 748.84 0.015 1 23.755 1 0.00714:28:59.25 336.35 23.153 483.21 0.032 0 764.24 1 0.007 114:28:38.72 23.458 573.55 23.772 0.011 1 1 1 23.779 97.2714:29:14.22 22.952 317.71 0.015 0.009 1 1 578.13 0.00714:28:35.87 0 133.16 23.786 0.011 1 1 23.987 1 1 23.801 190.514:29:46.01 417.96 1 23.23 0.008 1 1 1 0.022 57.38 0.00914:29:24.68 739.91 1 23.835 1 23.343 446.84 1 0.013 114:29:11.54 23.691 760.98 1 23.863 0.007 1 0 257.91 1 0.015 23.929 1 114:29:21.28 1 0.024 0.007 232.4 1 23.417 373.09 1 23.942 1 0.008 114:29:14.72 542.24 1 24.119 1 0 0.016 23.972 0.8 1 0.007 114:29:17.73 650.49 24.393 189.01 0 0.3 1 1 582.31 0.021 0.008 114:29:21.98 1 23.886 1 24.008 0.027 420.4 0.2 1 611.95 24.014 114:29:02.98 0.3 1 24.364 780.41 1 0.016 0.009 1 0.3 1 0.2 24.091 1 0.008 014:29:16.59 459.66 1 707.19 1 0.028 0.3 0 22.861 701.32 0.4 1 0.009 0 114:29:49.91 24.171 400.61 1 24.132 1 738.07 0.2 0.011 24.133 0.3 1 114:29:11.57 0 24.328 630.82 1 0.15 0.028 0.008 1 464.72 0.3 24.165 0.009 1 114:29:07.74 37659734 1 753.48 0.036 0.1 1 655.48 1 1 23.24 101298266 24.169 0.15 1 0.009 014:28:25.26 0.1 23.719 410.96 0.3 1 604.28 0 1 24.175 candidate 1 114:28:02.84 24.155 YSG 0.011 0.01 733.43 0.16 0.018 candidate 1 562.46 0.1 1 1 YSG 24.197 114:27:48.80 0.01 770.28 1 0.12 0.027 0 38090981 1 24.503 591.73 0.3 24.229 0.01114:29:16.63 candidate 0 0.3 211.81 YSG 1 0 0.1 1 1 23.126 candidate 154.13 1 0 0.034 YSG 24.261 0.01214:28:10.10 37481267 24.442 0.2 candidate 472.7 0 1 1 572.49 YSG 1 0 0.013 24.282 0.2 0.009 014:28:55.63 24.604 1 0.027 0.12 658.1 9143332 24.366 0.2 candidate 1 0.008 114:28:20.85 24.476 YSG 217.02 0 55.62 1 0.04 0 1 candidate 1 YSG 0.2 1 0.00914:29:06.23 661.55 0.1 24.251 649.63 1 1 0.2 0.03 1 0 80158243 212.81 1 24.376 0.15 014:29:00.70 24.682 755.59 24.428 0.021 0 24.444 442.5 0.014 0.3 1 114:28:06.78 0.1 1 729.19 0 0.025 0.012 0 17221257 candidate 0 104.12 0.3 YSG 0.1 1 0.009 014:29:04.10 1 265.61 0 24.65 4800577 24.501 0.6 1 1 24.374 512.11 candidate 1 24.519 BSG 14:29:20.84 0.3 23.216 316.68 0.009 0 0.3 1 635.21 0.037 0.035 24.529 0 114:28:22.82 67101111 0.2 0 candidate 0 0.01 702.07 0 YSG candidate 0.3 0.01 24.583 434.65 0.4 YSG 24.531 0.011 0 014:28:42.64 1 1 184.2 1 24.745 725.89 0.2 1 0.027 24.579 1 0.2 1 0.00914:29:09.55 23.815 116.86 0.7 54253155 0.3 1 0 0.031 24.653 1 1 0.015 1 114:29:30.78 34392135 23.924 665.77 255.9 0.016 0.7 334.59 0 1 0.014 1 014:28:55.25 37053207 0.3 23.686 384.46 0 0.015 1 595.38 0.7 24.668 24.779 114:28:05.68 0 26608022 candidate 1 25.509 0.18 300.13 YSG 0 0.8 0.03 1 1 774.15 0.7 0 24.808 0.01314:28:42.86 0.01 1 168.47 0.085 0 0.1 1 1 24.968 76.32 0.017 1 81341135 0.1 0 24.847 147.87 1 25.069 629.23 0.2 1 0.1 1 0.027 1 1 24.209 1 1156563 25.035 0.059 1 1 195.42 0.2 0.033 1 25.062 0.7 1 23.337 0.028 0.014 1 0.6 80781554 1 101298266 25.326 1 1 0.2 0.03 0.018 1 25.172 1 1 1 0.5 0.018 1 1 24979858 0.1 1 candidate 1 1 24.189 0.4 RSG 1 1 0.054 0.7 candidate 25.713 0.18 RSG 16384262 1 1 0 0.02 0.4 0.076 0 1 0.5 1 0 1 1 0 93054781 0.5 0.2 1 0 1 1 1 1 1 62222454 1 0.3 1 0.4 0.3 1 1 61828036 1 1 0.5 0 0 1 1 0.3 0.6 0 0.5 1 1 0 0.4 0.6 candidate 1 RSG 0 0.3 0 1 0 0.7 1 0.8 0.6 1 0 1 0.3 0.3 1 0 0.6 82850503 0.2 0 0 0 0.3 1 0 1066919 0.4 0.6 0.25 0 0.3 0.4 0.2 0.4 0 1 24979858 0.4 1.0 0.7 34077973 45607617 0.4 0.2 10916330 1.0 101291878 0.4 0.2 candidate RSG candidate RSG candidate RSG + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + –Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcseconds. Numbers 1 or 0 in columns MAD, IQR (J2000) (J2000) (pixels) (pixels) (mag) (mag) (mag) (mag) (mag) (mag) Properties of the variable candidates in NGC 4548 ordered by average magnitudes. For convenience we use the letter "V" to name each variable in this field. Note. and inverse von Neumann ratioshow the show amplitude whether of the variability. star was characterized as a variable in the respective index. Units of X and Y are pixels coordinates. Columns V2V3 12:35:23.771 V4 12:35:23.915 V5 12:35:23.013 V6 12:35:27.705 V7 12:35:25.186 V8 12:35:23.904 V9 12:35:23.891 V10 12:35:27.176 V11 12:35:24.934 V12 12:35:26.099 V13 12:35:30.830 V14 12:35:23.131 V15 12:35:25.854 V16 12:35:24.552 V17 12:35:29.507 V18 12:35:28.881 V19 12:35:31.087 V20 12:35:23.911 V21 12:35:30.115 V22 12:35:26.724 V23 12:35:24.753 V24 12:35:27.062 V25 12:35:31.169 V26 12:35:22.983 V27 12:35:23.487 V28 12:35:25.874 V29 12:35:24.065 V30 12:35:31.669 V31 12:35:25.647 V32 12:35:23.461 V33 12:35:23.869 V34 12:35:25.452 V35 12:35:29.360 V36 12:35:23.873 V37 12:35:27.937 V38 12:35:24.244 V39 12:35:24.039 V40 12:35:25.798 V41 12:35:23.614 V42 12:35:29.994 V43 12:35:31.146 V44 12:35:23.513 V45 12:35:29.497 V46 12:35:30.754 V47 12:35:23.904 V48 12:35:25.380 V49 12:35:28.770 V50 12:35:25.094 12:35:29.779 IDV1 RA 12:35:24.398 Dec X Y V Table 9.

Article number, page 12 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548 I ∆ and V ∆ I HSC MatchID Notes ∆ V ∆ I , V η / 1 I IQR V IQR I MAD V MAD I σ I V σ 14:28:54.9914:28:13.03 210.5214:28:59.88 137.44 339.6914:28:18.98 275.38 25.587 429.014:28:33.71 385.91 425.32 0.02314:27:19.47 503.13 25.608 386.15 25.62514:29:08.38 25.135 0.022 693.9 25.688 78.94 0.02314:29:02.13 452.94 0.051 24.879 0.01914:29:11.74 24.904 719.99 25.946 419.3 0.032 361.414:28:41.69 26.012 386.03 0.038 0.031 1 530.64 25.96614:27:55.20 26.091 0.073 66.55 26.304 26.141 478.0 0.025 114:29:06.10 354.35 0.033 1 0.107 0.03814:29:20.04 25.242 526.41 480.85 26.141 1 25.595 289.31 114:28:03.96 25.706 0.037 474.94 26.235 0.036 515.56 0.068 26.271 114:29:27.10 1 552.02 0.043 0.08 25.511 460.05 1 26.276 0.03914:29:05.78 630.57 1 1 25.309 759.99 1 0.068 114:29:18.85 26.32 25.891 0.05 753.83 0.055 26.328 64.66 1 114:29:00.57 1 479.41 0.076 0.051 1 26.604 575.9 1 0.03414:28:08.19 340.17 1 26.332 1 1 25.777 538.61 0.206 114:29:17.72 1 27.163 558.55 26.427 0.051 1 594.99 1 0.097 26.446 114:28:46.83 1 184.36 1 0.192 0.047 26.002 666.14 26.482 0 0.048 014:29:10.13 1 625.31 1 1 25.662 574.13 0.124 1 0.047 114:28:23.79 26.49 0 26.17 0 1 1 74.0 1 0.087 26.564 587.7 1 114:28:40.69 26.341 125.42 0.038 0.2 0.105 1 0.067 1 114:28:59.25 1 1 214.01 26.589 214.24 0.13 26.148 174.45 1 0.8 1 114:28:59.14 0 26.253 474.57 0.068 0 1.2 1 686.13 0.8 1 1 0.079 26.602 26.59 114:28:28.12 597.15 0.163 0.6 446.04 1 26.631 1 1 0.054 014:28:03.40 24.4 0.6 0 572.92 0.047 0 225.25 0.8 1 0.25 26.637 1 0.051 014:29:10.84 75035962 1 26.342 0 436.1 1 26.432 1 1 778.77 0.6 0.035 26.641 0.06114:29:12.13 0 26.392 323.91 0.121 0.25 0.5 1 91122684 0.125 0 26.652 1.2 0.049 014:27:47.31 31722844 193.41 1 26.798 416.72 0.139 0 0 794.9 1 1.2 0.063 0 114:28:08.09 34197730 1 25.918 254.41 1 26.664 0.207 1 0.6 36455381 1 370.9 1 0.6 014:29:11.46 1.2 26.071 613.92 26.684 0.073 0.055 0 1 0 95.08 1.2 114:28:11.03 0.6 762.25 26.693 0.091 0.069 0 0.8 1 26.011 607.01 0 1 114:28:01.16 1 0.7 356.71 26.704 0.054 55406013 1 1 26.706 376.03 1 0 0.105 26.706 0.314:29:06.83 1 1.2 232.23 0 42502132 1 25.455 558.55 0.8 0.06 1 1 26.734 0.7 0.07314:28:22.92 0.2 394.62 0 0.8 556.86 1 1 0.052 1 1 0.05914:28:57.75 26.75 0.5 26.036 1 26.35 89.12 0 32643206 0 195.08 1 26.776 0 0.614:28:23.79 34523449 0.5 25.193 672.09 0.142 0.045 0 1 0.2 0.134 1 26.808 1 0.2 114:29:04.07 188.84 0.06 0.049 candidate 79.33 0 1 26.013 474.96 1 RSG 0.7 0.067 014:27:25.30 0.5 0 334.28 0 26.851 1 1 26.857 1 0.074 26.885 1 0.814:28:07.01 229.97 0.8 25.403 688.36 1 0.057 1 0 348.89 0.181 0.5 0.07214:28:20.44 0 0.8 1 136.77 1 26.933 0.058 0 1.0 72878727 25.173 179.47 26.939 1 0 0 0.8 26.094 411.91 0 0 0.067 95680813 707.95 1 0.043 26.944 1 0.069 0 1 0.9 0 0.099 1 26.266 347.92 1.6 1 1345627 27.018 0.6 0 0.061 1 0 26.073 0.7 26832370 0 0.109 0.8 1 0.072 1 27.21 1 26.356 0.104 0.8 1 1 1 0.2 1 0 25.594 0.092 0.063 0.2 1 0 0.7 1 1 1 0.2 0.062 0 0.8 1 26.889 0.2 0 0 107997074 1 0.8 1 1 0.2 0 0.148 0 0 0 1 1 0 0.4 candidate 1.0 RSG 0 0.8 1 0 1 1 1 1080337 1 1 0 0 0.4 0.6 0 0.9 0 0 0 0 1.0 0 0 0.2 0.8 0.0 0 0 0.75 0 98942748 1 0 0 0.9 0 0.75 0.6 0.8 0 0 0.8 0 0 1 0.8 103939316 50783506 0.7 0 0 0.8 0 0.7 0.4 candidate 0.9 0 RSG 0 0.8 1 0.2 0.9 96500353 0.6 0 0.2 0.6 0.5 0.8 59753525 0.6 0.5 0.5 0.5 candidate RSG candidate RSG 83982657 candidate RSG + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + (J2000) (J2000) (pixels) (pixels) (mag) (mag) (mag) (mag) (mag) (mag) – Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcseconds. Numbers 1 or 0 in columns MAD, IQR Table 9 continued. Note. and inverse von Neumann ratioshow the show amplitude whether of the variability. star was characterized as a variable in the respective index. Units of X and Y are pixels coordinates. Columns V52V53 12:35:26.377 V54 12:35:31.141 V55 12:35:30.198 V56 12:35:30.355 V57 12:35:27.270 V58 12:35:29.997 V59 12:35:23.638 V60 12:35:31.340 V61 12:35:32.108 V62 12:35:27.631 V63 12:35:25.254 V64 12:35:31.095 V65 12:35:30.950 V66 12:35:28.238 V67 12:35:23.349 V68 12:35:32.131 V69 12:35:31.675 V70 12:35:30.909 V71 12:35:27.149 V72 12:35:23.592 V73 12:35:24.195 V74 12:35:27.714 V75 12:35:28.198 V76 12:35:32.971 V77 12:35:25.396 V78 12:35:30.742 V79 12:35:31.022 V80 12:35:29.361 V81 12:35:33.540 V82 12:35:27.177 V83 12:35:28.751 V84 12:35:24.356 V85 12:35:30.224 V86 12:35:25.665 V87 12:35:29.430 V88 12:35:27.902 V89 12:35:24.036 V90 12:35:27.591 V91 12:35:30.546 V92 12:35:28.862 V93 12:35:24.528 12:35:30.246 IDV51 12:35:27.325 RA Dec X Y V Table 10.

Article number, page 13 of 28 A&A proofs: manuscript no. aanda

Fig. 1. Histogram of the number of sources in filters V and I in NGC 1326A, NGC 1425, and NGC 4548. The blue and red dashed vertical line correspond to the magnitude in V and I, respectively where our sample reaches 50% completeness.

Article number, page 14 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

Fig. 2. The difference between input and output magnitudes as a function of the output magnitude for NGC 1326A, NGC 1425, and NGC 4548. The dashed line indicates the 50% completeness magnitude.

Article number, page 15 of 28 A&A proofs: manuscript no. aanda

21 BSGs YSGs RSGs 20M ¯ 15M ¯ 10M ¯ 8 22 V1 8M ¯ V2 V3 V4V5 V6 V7 7 23 V9 V8 V10

V11 ) V12 V13 g 6 a V14 24 m (

V15 V V16V17

V (mag) V18

V19 M V20 V21 5 V22 25 V26V23V25 V24 V27 V29V28V32V33 V31V30 V36 V34 V35 V38 V37V39 V42V40 V41 4 V44V45 V47 V46 V43 26 V48 3 27 0 1 2 3 4 V I (mag) −

Fig. 3. Top panel: V−I versus V color-magnitude diagram of NGC 1326A. Both absolute and mean magnitudes of the stars are plotted on the y-axis, based on the distance modulus 31.04 mag. The constant stars are shown in gray, the known Cepheids as blue triangles and the new candidate variables as black dots. Bottom panel: Spatial distribution of the candidate variable sources in NGC 1326A.

Article number, page 16 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

19 BSGs YSGs RSGs 27M ¯ 1 20M 9 ¯ 20 15M ¯ V2 10M V4V3 ¯ V5 8M 8 21 ¯ V6 V7 V9 V10V8 12V14 V11V13

22 7 )

V15 g

16 a V17 V18 19 2120

V22 V23 m 23 25 26 V2827 V24 29 30 ( V32V34 31 V33 V36 V37 V35 6 V

V (mag) V39V38V40 24 43 V42V41 M V44 V46 V45 50V48V49 V47 54 V51 V53V52 V58 55 V56V57 V61596466 V6562 60 V63 5 67 V69 V70 68 25 V757681797778V74V73 V71V80V72 91V8783V92 94 88 V86V82V84V9385 V89V90 V97 95 98 99 V96 100 102101 26 4

1 0 1 2 3 V I (mag) −

Article number, page 17 of 28 Fig. 4. Same as Fig 3, for NGC 1425. A&A proofs: manuscript no. aanda

BSGs YSGs RSGs 20M ¯ 15M ¯ 21 10M V1 ¯ 8 8M V2V3 ¯ V5V6 V4 V9 V7 V8 V11 V10 V12 22 V18V13 V16 V17V15V14 V19V21 V23 V20 V22 V24 V27 V26 V25 7 V31V28V30V32 V29 V34V35 V33

V36 ) V39V38 V41V40V42 V43 V44 g 23 V45

V46 a V48 V49 V47

6 m

V50 (

24 V51 V53V52 V V (mag) V54 M V55 V56 V57 5 V58V59 V60 V64 V62 V65V61V63 V67 V66 25 V68V70V69 V75 V72V74V73 V77V78V76 V71 V85V79 V81 V82V84 V80 V83 V88 V86 V87 V91V89V90 V92 4 26 V93

27 3 0 1 2 3 4 V I (mag) −

Fig. 5. Same as Fig 3, for NGC 4548.

Article number, page 18 of 28 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

Fig. 6. Left column: Blue to red supergiant ratio for NGC 1326A, NGC 1425 and, NGC 4548. The dashed red line is a linear fit indicating the monotonic radial decline of the blue to red supergiants. Right column: Spatial distribution of the blue and red supergiants. The radius of each of the white annuli displayed shows the distance in respect to the center of each galaxy.

Article number, page 19 of 28 A&A proofs: manuscript no. aanda

22 23 24 25 26 103 12000 NGC 1326 5 6 18 28 70

NGC 1326 10000 2 −

c 8000 p k ) 1 − r

y 6000 M

¯ log count M ( R

F 4000 2 10 S

2000

0 10 9 8 7 6 5 4 10 20 30 40 50 60 70 MV (mag) Age (Myrs) 22 23 24 25 26 27 103 9000 NGC 1425 7.9 10 15 25 45 60 100 8000 NGC 1425 7000 2 −

c 6000 p

2 k )

10 1

− 5000 r y M

¯ 4000 log count M ( R

F 3000 S 2000 101 1000

0 8 7 6 5 20 40 60 80 100 MV (mag) Age (Myrs) 21 22 23 24 25 26 27 103 12000 NGC 4548 7 8 10 30 40 50100

NGC 4548 10000 2 −

c 8000 p k ) 1 − r

y 6000 M

¯ log count M

2 ( 10 R

F 4000 S

2000

0 10 9 8 7 6 5 20 40 60 80 100 MV (mag) Age (Myrs) Article number, page 20 of 28 −1 −2 Fig. 7. Left column: SFR in M Myr kpc for NGC 1326A, NGC 1425, and NGC 4548 over the last 100 Myr, based on the blue HeB stars. The blue HeB luminosity function has been normalized to account for the IMF and the changing lifetime in this phase with mass. We used the Salpeter IMF slope and the MESA evolutionary tracks. Right column: Luminosity function of the Blue HeB stars in NGC 1326A, NGC 1425, and NGC 4548. The bin width is 0.18 mag. The uncertainties in magnitude are derived by the artificial star tests. Plotted above the histogram is the age in Myrs for the blue HeB stars as given by the MESA models. Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

0.40 NGC 1326A

0.35

0.30

0.25

MAD V 0.20

0.15

0.10

0.05

23 24 25 26 27 V (mag)

NGC 1425 0.35

0.30

0.25

0.20 MAD V

0.15

0.10

0.05

23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 V (mag)

NGC 4548

0.4

0.3 MAD V 0.2

0.1

23 24 25 26 V (mag)

Fig. 8. Mean absolute deviation versus mean magnitude for the WF3 chip in NGC 1326A, NGC 1425 and NGC 4548. The dashed line shows the stars over the 4σ threshold. The variable candidates are shown in red squares and the known variables are shown in blue triangles.

Article number, page 21 of 28 A&A proofs: manuscript no. aanda

V1 V2 V11 V12 26.00 26.00 23.50 24.80 26.25 26.50 24.00 24.90 26.50 27.00 24.50 25.00 26.75 27.00 27.50 24.50 22.40 23.80 24.60 22.90 22.50 23.90 24.70 23.00 22.60 24.00 24.80 23.10 22.70 24.90 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V3 V4 V13 V14 25.60 26.00 24.70 26.40 25.70 26.40 24.80 26.80 25.80 26.80 24.90 27.20 25.90 27.20 25.00 27.60 24.16 24.00 23.70 24.25 23.80 24.50 24.24 24.08 23.90 24.32 24.16 24.00 24.75 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V5 V6 V15 V16 26.70 26.40 26.40 27.00 27.00 26.70 27.25 27.30 27.00 26.80 27.50 27.30 27.20 27.60 27.60 23.80 23.92 24.30 24.90 23.90 24.00 24.45 25.20 24.00 25.50 magnitude 24.08 24.60 magnitude 24.10 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V7 V8 V17 V18 24.00 26.40 26.40 24.40 24.75 26.70 26.80 24.80 24.90 27.00 27.20 25.20 27.30 25.05 27.60 27.60

24.00 23.25 25.00 24.75 24.10 23.40 25.25 25.00 24.20 25.25 25.50 24.30 23.55 25.50 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V9 V10 V19 V20 25.20 26.70 24.90 26.80 25.60 27.00 25.00 26.00 27.30 27.20 25.10 26.40 27.60 27.60 22.60 24.90 23.92 25.20 24.90 24.00 22.66 25.50 25.20 24.08 22.72 25.80 25.50 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

V21 V22 V31 V32 25.00 25.60 25.20 24.40 25.20 26.00 25.60 24.50 25.40 26.40 26.00 24.60 25.60 26.80 26.40 24.70 24.00 25.20 24.80 24.40 24.20 25.50 25.20 24.80 24.40 25.80 25.60 25.20 24.60 26.10 26.00 25.60 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V23 V24 V33 V34 24.00 24.00 24.05 25.60 25.80 24.10 24.20 26.00 26.40 24.15 24.40 26.40 24.20 26.80 27.00 24.80 24.00 25.25 24.60 25.20 24.50 25.50 25.20 25.60 25.00 25.75 25.50 25.80 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V25 V26 V35 V36 24.00 23.90 26.00 25.60 24.08 24.00 26.50 26.00 24.16 24.10 27.00 26.40 24.24 24.20 24.80 25.20 25.50 25.60 25.80 25.20 25.60 26.00 26.00 26.10 25.60 26.40

magnitude magnitude 26.40 26.40 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V27 V28 V37 V38 24.16 24.20 26.00 26.00 24.24 24.30 26.40 26.40 24.32 24.40 26.80 26.80 24.40 27.20 27.20 24.80 25.50 25.60 25.20 25.75 25.80 25.60 25.60 26.00 26.00 26.00 26.40 26.25 26.20 26.50 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V29 V30 V39 V40 24.80 26.00 24.30 26.00 26.40 24.40 25.20 26.40 26.80 24.50 25.60 26.80 27.20 24.60 26.00 24.90 25.20 25.60 25.80 25.20 25.60 25.80 26.10 26.00 25.50 26.00 26.40 26.40 25.80 26.20 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

Article number, page 22 of 28 Fig. 9. Light curves of the candidate variables in NGC 1326A. The V filter is shown in filled blue circles and the I filter in red squares. Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

V41 V42 V1 V2 25.80 26.00 22.60 23.30 26.40 26.40 22.64 23.40 27.00 26.80 22.68 22.72 23.50 27.60 27.20 22.16 22.70 25.80 25.60 22.24 22.80 26.00 26.00 22.32 22.90 26.20 26.40 26.40 22.40 23.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V43 V44 V3 V4 26.00 26.00 23.50 23.50 26.50 26.40 23.55 23.55 27.00 26.80 23.60 23.60 27.50 27.20 23.65 23.65 22.90 22.92 25.60 25.20 22.96 22.96 25.80 25.60 23.00 26.00 26.00 23.02 23.04 26.20 26.40 23.08 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V45 V46 V5 V6 24.80 25.80 23.60 23.86 25.00 26.40 23.68 23.76 23.92 25.20 27.00 25.40 23.84 23.98 27.60 25.80 25.80 23.12 23.30 26.00 26.00 23.20 23.40 26.20 26.20 23.28 23.50

magnitude 26.40 26.40 magnitude 23.60 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V47 V48 V7 V8 25.60 26.40 23.80 26.70 23.80 26.00 23.90 27.00 23.90 24.00 26.40 27.30 24.00 24.10 26.80 27.60 24.10

25.80 26.00 23.70 22.60 22.80 26.10 26.50 23.85 23.00 26.40 27.00 24.00 23.20 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V9 V10 23.90 23.92 24.00 24.00 24.10 24.08 24.20 23.70 23.00 23.75 23.05 23.10 23.80 23.15 23.85 23.20 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d)

V11 V12 V21 V22 24.10 25.20 24.10 24.20 25.20 24.20 24.30 25.30 25.35 24.30 24.40 25.40 25.50 24.50 25.50 25.20 23.50 23.85 24.60 25.40 23.60 24.00 24.70 25.60 23.70 24.15 24.80 23.80 25.80 24.30 24.90 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V13 V14 V23 V24 24.16 25.20 24.20 25.20 24.24 25.40 24.30 25.35 24.32 25.60 24.40 25.50 24.40 25.80 23.52 23.80 24.60 23.00 23.60 23.90 24.80 23.10 24.00 25.00 23.68 23.20 24.10 25.20 23.30 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V15 V16 V25 V26 24.90 25.20 24.60 25.30 25.05 24.80 25.40 25.40 25.00 25.20 25.60 25.50 25.20 25.35 25.80 25.60 24.40 25.00 24.75 25.00 24.60 24.90 25.25 25.20 24.80 25.05 25.50 25.40 magnitude 25.00 25.20 magnitude 25.75 25.60 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V17 V18 V27 V28 24.50 25.20 25.20 25.00 24.75 25.40 25.50 25.20 25.00 25.60 25.40 25.25 25.80 25.50 25.80 24.40 24.30 24.60 24.48 24.50 24.60 24.70 24.56 24.75 24.90 24.80 24.64 24.90 25.00 25.20 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V19 V20 V29 V30 25.20 25.10 25.10 25.40 25.40 25.20 25.20 25.60 25.60 25.30 25.30 25.40 25.80 25.80 25.40 25.00 23.00 25.20 24.40 24.80 23.10 25.40 24.60 25.00 23.20 25.60 24.80 25.20 23.30 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

Article number, page 23 of 28 Fig. 10. Same as Fig. 9 but for NGC 1425. A&A proofs: manuscript no. aanda

V31 V32 V41 V42 25.35 25.80 25.80 25.50 25.50 25.75 26.10 26.00 25.65 26.00 26.40 26.20 25.80 26.40 24.90 24.90 25.20 25.50 25.00 25.20 25.75 25.25 25.50 26.00 25.50 25.50 25.80 25.80 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V33 V34 V43 V44 25.50 25.40 25.80 26.00 25.75 25.60 26.10 26.25 26.00 25.80 26.50 26.40 26.00 24.40 24.40 25.00 24.60 24.90 24.60 25.20 24.80 25.20 24.80 25.40 25.00 25.00 25.50 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V35 V36 V45 V46 25.20 25.50 25.60 26.10 26.10 25.80 25.80 26.40 26.40 26.10 26.00 26.70 26.40 26.20 26.70 24.40 25.00 24.90 24.80 24.60 25.25 25.20 25.00 24.80 25.50 25.50 25.75 25.20 magnitude 25.00 magnitude 25.80 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V37 V38 V47 V48 25.20 25.60 26.00 25.50 26.10 25.80 26.00 26.40 26.40 26.10 26.40 26.70 26.80 24.90 24.90 25.20 25.00 25.20 25.20 25.50 25.25 25.80 25.50 25.50 26.10 25.50 25.80 25.80 26.40 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V39 V40 V49 V50 25.50 26.00 26.00 25.75 25.75 26.00 26.40 26.40 26.25 26.00 26.80 26.80 26.50 26.25 27.20 27.20 24.80 25.50 24.75 25.50 25.20 25.75 25.00 25.80 25.60 26.00 25.25 26.10 26.25 25.50 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

V51 V52 V61 V62 26.00 26.00 26.25 26.00 26.40 26.40 26.50 26.40 26.70 26.80 26.75 26.80 27.00 27.20 27.00 25.00 25.00 25.20 25.25 25.25 25.50 25.50 25.50 25.50 25.75 25.80 25.75 25.75 26.00 26.00 26.00 26.10 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V53 V54 V63 V64 26.00 26.00 26.00 26.40 26.40 26.40 26.40 26.80 26.80 26.80 26.80 27.20 27.20 27.20 27.20 25.50 25.20 25.05 25.20 25.75 25.50 25.50 25.20 25.80 26.00 25.80 26.25 25.35 26.10 26.10 26.40 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V55 V56 V65 V66 26.00 26.00 26.00 26.40 26.40 26.50 26.40 26.80 26.80 27.00 26.80 27.20 27.20 27.50 27.20 25.50 25.20 25.50 25.20 25.80 25.60 25.75 26.00 25.60 26.10 26.00 magnitude 26.00 magnitude 26.40 26.40 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V57 V58 V67 V68 26.00 26.40 26.00 26.40 26.40 26.70 26.50 26.80 26.80 27.00 27.00 27.20 27.20 27.30 27.60 25.20 25.00 25.20 25.50 25.50 25.50 25.50 25.80 25.80 26.00 25.80 26.50 26.10 26.10 26.10 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V59 V60 V69 V70 26.00 26.00 26.40 26.50 26.40 26.50 26.80 26.75 26.80 27.00 27.20 27.00 27.20 27.50 27.60 25.20 25.20 25.20 25.50 25.60 25.60 25.40 25.75 26.00 26.00 25.60 26.00 26.40 26.40 25.80 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

Article number, page 24 of 28 Fig. 10. continued Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

V71 V72 V81 V82 26.40 26.40 26.40 26.40 26.70 26.80 26.80 27.00 26.80 27.20 27.20 27.20 27.60 27.30 25.20 25.50 25.20 25.60 25.50 25.50 26.00 25.80 25.80 25.80 26.10 26.40 26.10 26.10 26.40 26.40 26.40 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V73 V74 V83 V84 26.40 26.40 26.50 26.40 26.70 26.70 26.75 26.70 27.00 27.00 27.00 27.00 27.30 27.25 27.30 27.60 27.30 27.60 24.80 25.50 25.60 25.60 25.20 25.75 25.80 26.00 25.60 26.00 26.00 26.40 26.00 26.25 26.20 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V75 V76 V85 V86 26.40 26.40 26.40 26.40 26.70 26.70 26.80 27.00 26.80 27.20 27.30 27.00 27.20 27.60 27.60 27.30 27.60 25.20 25.50 25.20 25.50 25.60 25.60 25.80 25.80 26.00 26.00 26.10 26.40 26.10

magnitude magnitude 26.40 26.40 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V77 V78 V87 V88 26.40 26.40 26.40 26.50 26.70 26.70 27.00 27.00 27.00 26.80 27.50 27.30 27.20 27.60 27.30 25.50 25.50 25.50 25.50 25.75 25.75 26.00 26.00 25.80 26.00 26.50 26.25 26.10 26.50 26.40 26.25 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V79 V80 V89 V90 26.40 26.40 26.70 26.40 26.40 26.70 27.00 26.80 26.80 27.00 27.30 27.20 27.20 27.30 27.60 27.60 27.60 25.20 25.40 25.60 25.60 25.50 25.60 26.00 26.00 25.75 25.80 26.40 26.40 26.00 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

V91 V92 V101 V102 26.40 26.70 26.80 26.80 26.70 27.00 27.20 27.00 27.30 27.20 27.60 27.30 27.60 27.60 27.60 25.75 25.60 25.80 25.80 26.00 26.00 26.10 26.10 26.40 26.25 26.40 26.40 26.50 26.70 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V93 V94 26.40 26.80 26.70 27.00 27.20 27.30 27.60 25.50 -0.06 -0.03 25.80 0.00 26.10 0.03 0.06 20 40 60 80 100 20 40 60 80 100

V95 V96 26.50 26.70 26.75 27.00 27.00 27.25 27.30 27.50 27.60 25.80 26.00 24.90 26.20 25.05 25.20

magnitude 26.40 20 40 60 80 100 20 40 60 80 100

V97 V98 26.40 26.70 26.80 27.00 27.20 27.30 27.60 27.60 25.60 25.80 26.00 26.10 26.40 26.40 26.80 26.70 20 40 60 80 100 20 40 60 80 100

V99 V100 26.40 26.50 26.80 27.00 27.20 27.50 27.60

25.75 25.60 26.00 26.40 26.25 27.20 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d)

Article number, page 25 of 28 Fig. 10. continued A&A proofs: manuscript no. aanda

V1 V2 V11 V12 24.04 23.00 23.20 23.45 24.10 23.30 23.50 23.10 24.16 23.40 23.55 23.20 23.50 24.22 22.20 22.30 22.80 22.56 23.08 22.64 23.14 22.36 23.40 22.42 24.00 22.72 23.20 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V3 V4 V13 V14 23.40 23.30 23.30 23.60 23.60 23.40 23.40 23.80 23.70 23.50 23.50 24.00 23.80 22.30 22.56 23.80 22.85 22.40 22.64 23.90 22.90 22.50 24.00 22.60 22.72 22.95 24.10 22.70 22.80 23.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V5 V6 V15 V16 23.30 23.60 23.50 23.70 23.40 23.80 23.68 23.60 23.50 23.90 23.76 23.70 23.60 24.00 23.84 23.80 23.70 22.70 22.50 22.70 23.40 22.80 22.55 22.90 22.75 23.55 22.60

magnitude 23.00 magnitude 22.80 23.70 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V7 V8 V17 V18 24.45 23.55 23.52 23.80 24.50 23.70 24.55 23.60 23.90 23.85 24.60 23.68 24.00 24.65 24.00 23.45 23.60 23.50 23.36 22.65 23.68 23.40 23.55 22.80 23.76 23.60 23.44 23.84 23.65 23.48 22.95 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V9 V10 V19 V20 23.60 24.80 23.70 23.70 23.52 25.00 23.80 23.60 23.80 25.20 23.90 23.90 23.68 25.40 24.00 23.80 23.70 22.80 23.44 24.00 23.85 22.90 23.52 24.20 24.00 23.00 23.60 23.10 24.40 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

V21 V22 V31 V32 24.60 23.80 23.75 24.75 23.76 23.90 23.84 24.00 24.00 24.90 24.25 24.10 25.05 23.92 24.50 24.20 24.00 23.70 22.10 24.10 22.20 24.20 24.20 23.85 22.30 24.40 24.30 22.40 24.40 24.00 24.60 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V23 V24 V33 V34 23.80 23.90 23.92 23.90 24.00 24.00 24.00 24.00 24.25 24.10 24.08 24.10 24.50 24.20 23.80 24.20 23.90 23.84 23.90 24.30 24.00 23.92 24.00 24.10 24.40 24.10 24.20 24.00 24.50 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V25 V26 V35 V36 23.92 24.00 24.20 24.20 24.00 24.10 24.40 24.30 24.08 24.20 24.60 24.40 24.50 23.40 23.70 23.70 22.90 23.50 23.80 23.85 23.00 23.60 23.90 24.00 23.10

magnitude magnitude 24.00 23.70 24.15 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V27 V28 V37 V38 23.80 24.00 24.00 23.90 24.05 24.50 24.15 24.10 24.00 25.00 24.30 24.10 24.15 24.20 25.50 24.45 23.90 22.40 24.00 22.90 24.00 22.60 24.10 23.00 24.10 22.80 24.20 23.10 24.20 24.30 23.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V29 V30 V39 V40 23.90 23.80 24.00 24.00 24.00 24.00 24.10 24.20 24.10 24.20 24.20 24.40 24.20 24.40 24.30 24.60 24.40 24.00 22.72 24.00 23.36 24.40 22.80 24.15 23.44 24.80 22.88 24.30 23.52 25.20 23.60 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

Article number, page 26 of 28 Fig. 11. Same as Fig. 9 but for NGC 4548 Spetsieri et al.: Massive star population in NGC 1326A, NGC 1425 and NGC 4548

V41 V42 V51 V52 24.40 24.45 25.20 24.80 24.80 24.60 25.60 25.60 24.75 25.20 26.00 26.40 24.90 26.40 23.50 24.00 23.30 23.60 24.40 23.40 23.70 24.80 24.50 23.50 23.80 25.20 25.00 23.90 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V43 V44 V53 V54 24.50 25.20 24.20 25.20 24.75 24.40 25.60 25.50 25.00 24.60 25.25 26.00 25.80 24.80 26.40 24.40 23.20 24.30 24.50 24.40 23.40 24.60 24.80 24.60 23.60 24.70 25.20 24.90 23.80 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V45 V46 V55 V56 25.50 24.60 25.75 24.60 25.75 24.80 24.75 26.00 26.00 24.90 26.25 25.00 26.25 24.50 24.60 23.60 24.00 24.75 24.80 23.80 24.30 25.00 25.00 24.00 24.60 magnitude magnitude 25.25 25.20 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V47 V48 V57 V58 24.60 24.00 25.60 24.80 25.80 24.80 26.00 25.00 25.60 26.40 26.40 25.20 26.40 27.00 26.80 22.90 23.00 24.60 24.80 23.00 24.00 25.20 25.20 23.10 25.00 23.20 25.80 25.60 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V49 V50 V59 V60 24.80 24.40 25.60 25.00 24.80 25.60 26.00 25.20 25.20 26.40 26.40 25.40 25.60 27.20 26.80 23.40 24.00 23.70 24.80 24.80 24.10 24.00 25.20 25.20 24.20 24.30 25.60 25.60 24.60 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

V61 V62 V71 V72 25.60 25.00 24.80 26.00 26.00 25.60 25.20 26.40 26.40 25.40 26.80 26.80 26.40 25.60 27.20 25.00 25.00 24.00 24.80 25.25 25.25 24.20 25.20 25.50 25.50 24.40 25.60 25.75 25.75 26.00 24.60 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V63 V64 V73 V74 25.60 26.00 25.60 26.00 26.00 26.25 26.00 26.40 26.40 26.50 26.40 26.80 26.80 26.75 26.80 27.00 27.20 25.00 25.00 24.80 25.25 26.00 25.25 25.20 25.50 26.40 25.50 25.60 25.75 26.80 26.00 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V65 V66 V75 V76 25.50 25.80 26.00 26.00 25.80 26.40 26.40 26.40 26.10 26.80 26.80 27.00 27.20 24.80 25.20 25.00 24.60 25.40 25.25 25.20 25.20 25.60 25.50 25.60

magnitude 25.80 magnitude 25.80 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V67 V68 V77 V78 25.60 26.00 26.00 26.00 26.00 26.40 26.40 26.40 26.40 26.80 26.80 26.80 26.80 27.20 27.20 27.20 24.80 24.80 26.00 25.20 25.20 25.20 26.40 25.60 25.60 25.60 26.80 26.00 26.00 26.00 27.20 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

V69 V70 V79 V80 26.00 26.00 24.80 26.00 26.50 25.60 26.40 26.40 27.00 26.40 26.80 26.80 27.20 27.20 24.80 25.00 24.00 25.20 25.20 25.50 24.80 25.60 25.60 26.00 25.60 26.00 26.00 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d) HJD-2450200 (d)

Article number, page 27 of 28 Fig. 11. continued A&A proofs: manuscript no. aanda

V81 V82 26.00 24.00 26.40 25.00 26.80 26.00 27.20 27.00 25.20 24.00 25.60 24.80 26.00 25.60 20 40 60 80 100 20 40 60 80 100

V83 V84 25.60 26.25 26.50 26.40 26.75 27.20 27.00 28.00 25.20 25.25 25.50 25.50 25.75 25.80 26.00 26.10 20 40 60 80 100 20 40 60 80 100

V85 V86 26.00 25.20 26.40 25.60 26.80 26.00 27.20 26.40 24.80 24.00 25.20 24.40 25.60 24.80

magnitude 26.00 25.20 20 40 60 80 100 20 40 60 80 100

V87 V88 26.00 26.00 26.40 26.40 26.80 26.80 27.20 27.20 24.75 25.20 24.90 25.40 25.05 25.60 25.80 20 40 60 80 100 20 40 60 80 100

V89 V90 26.00 26.00 26.40 26.40 26.80 26.80 27.20 27.20 25.20 25.20 25.60 25.60 26.00 26.00 20 40 60 80 100 20 40 60 80 100 HJD-2450200 (d)

Fig. 11. continued

Article number, page 28 of 28